2 5 2 5 11111 10 I0 ~~ 111128 11111

p~ Illt~ 22 D p36~ III~I-

I I1 ~-t [~amp~ 11111

1111118 - 1111118

11111125 1114 11I1I~6 lilli 5 J 4 1111116

MICROCOPY RESOLUTION T[Sf CHAR1 MICROCOPY RlSOLUliON ITST CHART

FEBRUARY 1938TECHNICAL BULLETIN No 600

LNITED STATES DEPARTMENT OF AGRlCULTURi

WASHINGTON D C

THE INFLUENCE OF CLIMATE AND GRAZshyING ON SPRING-FALL SHEEP RANGE

IN SOUTHERN IDAHO I

By G V CUADDOCK ~eni()r range CJUiIIiner InlermotwlcIn forc~t (lnd Rrwgl Experiment Station and C L FOmnING Assistant Chief in charge Forest Resarch Forest ServIce 2

CONTENTS

Pngo (1 rIIting influences-ContinuedSignilitanre of springmiddotfall rungo sturlics DepIction frolll heny lore spring UJI(I lAicStudynrca ~ fnU JHItItug- ~ ~ _ ~_ w ~ ~~_~ ~c bull ~- _~_ - 27_ ___ _ ~ Methods of stud) _ J)eplction from modrntll 11110 spring und Climatic i n(uellccs ~~ bull ~ ~

Climate durilll( lhe 00

perio(l oC ~tudy 7 hell fnll gru7in( 10 Hunge improenwnl from Into fall grllljng Inllueuce or (llimaLC on ~ru1iug period~ 11

11 only __ -- 3~In(uence of Clilllllto 1)11 forn~c productionIn(uence of climu~e on nlll() shccp bullbull __ bull iii SiglliI~l1lte(Jfrnllgedclllcti(lnlhrou~lt ocrmiddot

Ilruting __ 35Qrazing inlluenccs _ _00 bullbullbullbull ~ ~~ I Rang depIction resuiting Crom hea conmiddot ) Rango JJ1UUtCIIIIlHO hy eOT1soryuthosllring and

tlnuousspring nnd lute full grazing filII gruzlI1g an Depletion from heny early spring nnd ialr

fnll graz1ng bullbull_-_bullbullbull middot 25 poundV~~~l~t~~~I~W~t~~I~~~~~~I_I~~ ~ ~ ~ ~_~~~ ~~ ~~ - ~rr

SIGNIFICANCE OF SPRINGmiddotFALL RANGI~ STUDmS

Ranges that n1e suitable for spring and inn grazing constitute a vital link in tbe year-round feed supply for range sheep production tblougilout a lnrge portion of the western Vnittd States As the name implies these lands fiTemiddot utilized for two importnnt grnzing periods each yefir-the first for se-NnJ weeks or months in the spring during and following Inmbing 1)(fo]e the high summer llllge is lelldy when succulent feed is eSlgtcntial to give lambs no ])roptl ftnlt in growth and development the seeond for nlike ptriocl in the fall when ewes should be attaining propel eonditionfol bngtecling nnd before snows force the fiorks to sheltered winttl ran~(s or feed lotf

The foothill ltmds of southeIll Idaho hn ve been found to be espeshycially well adapted fo1 meeting these spring and fall mnge requirements In the spring the fresh green bUIlrhgrllsses and weeds that grow in

I Received for publicatioll May 28 JD3i This study lliS mud possihle through II cpopcrntil ugreement willnby tIll Dunnu of Animallndustry

supplied livestock grazing arens IIn(1 nccommodntions for the Forrst Senice (cchoicillllS at the lnilcd Stales Sheep Experiwent Slntion llt~nr DuhoiS ldullo for tile (t yenrs of the study Very considerable assistnnce was contributed by W A Deneekc formcr superintendent n( th Shcl]l xperiment station in helping to plall tho study and In tnking und complliug records on numherlt of livestock grazed weights losses und ylolds during tho mujor purt Qf ~llo lost porlod During tile remainder of tho timo that the tesis ran ahle assitunce in recording compilint( nnd unalyzing similnr records wus rendered by his successor J M Cooper C L FOlllling was director of the Intermountain stalion during the pedod o( this study Weather data were ohtnined in cooperation with the Weather Bureau

li963-aS-l

2 TECHNlCAL BULLETIN 600 U S DEPT Q AGlUCLl~lUUB

mixture with sagebrush on these lands are highly nutritious andpalatable and what is not then consumed cures well during the drysummers and remains availllble for grazing in the fall The one cropof forage usullUy produced on these ltnds is th(refore suitable for thetwo grazing seasons (pI 1 A) In addition these lands liTe ceutrallylocated between the mountain summer range and valley winter rangeand feed lots and are characterized by a rolling topogrllphy thatsimplifies herding and enables close supervision of tJIC flocks duringthe critical periods of lambing and breedingFrom tho early days of settlement graziers htwc planned theiry6lLrly calendar of operatioIls in accordance with the IIvailn bility offorage today about 2000000 of the 6000000 sllCep thnt grazeannually within the IntelllIo11ntain region nre herded Over the footshyhill lands of southern Idaho during the spring and faU seWOIlS Tilegen~ral pluetice today as in earlier cltt)s is to tU)n sheep on the range

IlS soon as forage become available in the spring hold the flocks therelllltil summer range is f lndy and TetUIll them in the fall to utilizeremaining fOJflgeIn leeenli years iIlereased eompetition for range and tbe reCUllClIceof drought lave 1es1l1 kd in an intensified use of foothillllllds to thedetriment of the J1llIge reSource In an effort to shorten the winterfeeding period and to exclude competing herds from the ltLuge it hasbeeome It common p1lctice for example for operators to commencegrazing tb(ir sheep as soon as )Jant growth starts in tIle spring and toutilize nearly n11 of the forage dlUing the spring period Jeaving littleor none for fall Severe oTergruzing has resulted aod as a conseshyquence extensive areas of spring-fall )Hnge lands art in n seriouslydepleted condition and the possibilities for profitable range sheepproduetion are grelltly dimiIlisbcdClearly if the spring-fall mnge lands of SOlltJ)(jJl Idaho arc to conshytinue to be profituble for range sheep produ(tion the extent to whichthese lttnds call he gmztd without dctlimen tal di(Cts In list he ascershytained and improved systems of manngemellt bllS(( on the knownlimitations IlDd pottntinlities of the forage J(SOllrce put into effectAs It first step in this direetion this Jepolt prcstnts the results ofstudirs (xEuding ov(l the 9-year p(liod 1924-32 Oil the influ(lJ(C ofclimnte and grlLzing on the sagcbrush-wbentgmss range type nt theUnited Stl1t(S She(p Experiment Station The major phases of thesestudies include (1) The inflllenee of dimate more (spcrinlIy t(mshyperature and pleeipitntion on the periods of mnge lise unmwl forageproduction and the productivity of muge sheePi (2) thn effects ofdifferent inttnsitics of spring grazing on fornge production and thenatural rcregetntion of the bunehgrnss unci oti1fl types of forage inthe sngebrusL-wbpatglass 1Iwge type and (3) the development ofprinciples of managpJll(gtJIt based on Tesluts of these studies which itwould be desirahle to apply to spring-fltll range fol the most effectiveconservationanduse of the forage for range sheep production

STUDY AREA

The United States Sheep Experiment Station loeated near thenortheastern extremity of the SIlItke RiYer plains of south(rIl Idaho(fig 1) at an eJevation ranging from 5500 to 6000 fpet covers 28160acres of which 16640 aeres was under fence during the study In

Tedic1 Bulletin (00 l S Dept I Agriculture PLATE 1

EWES AND LAMBS ON SPRtNG-FALL RANGE

t 1))(1 I-ru-OIs HlIel wImiddotId that JU~IW ill luixtllrp ith ~lWfhr[Jsh HilI nOwr -hruhs nrl ftlishlll hy ~Iwtp m Ill ~pnm IHid rallllwi (unslIIUI all itnlorlanl hllk 11 Ii ~armiddotrollht rtI(t supply rqr rnnVll-slt(middotp prOdUlllOtl ill fo(owllllJI fdn~HJ IJ ~htPlf OJI fh~ joflprrathply ~tiltd tx(llriflIl1I1~$tllli()1I raBIH Hlt mllinlHiJwd ill flJlJnS toudUlull Hlld prodWl (Olhlllllly Idlh IUlllh (ropl Hlltl Sithl~ (If wool

3 INFLUENCE OF GHAZING ON SPlUNG-FALL SHm~p HANGE

comparatively recent geologic times a lit fl flow coyered the entire station range and surrounding territory creating a f1nt to gen tly rolling surface on which a sundy loam soil a few inches to seyerl)l feet in depth has deyeloped The nrelt is rrndily accessiblr to linstock but beshycause of the absence of surfnee Wlltrr except where an intermittent stream crosses the northwest corner of the property jt is necessary to haul wnter to the sheep from 11 deCp well at headqunrtrrs

Temperatures nre grIlernlly fnxorahle for plnnt growth from early April untillnte OctohCr Prf1ripitntion rnrrly ex(Ceds 15 inches nnshyllunlly SOlllcwhnt kRR tJltI1l half of the pre(ipitutioll oeems HS snow

-T-~----------------------~ i I i

- t1 0 j

$

bull p---- ---

I I i A )_~ 0 R bull 0 0

amp i i e o~

~ L---~---r- ~ ~~ I ~ - r ~ SAGe8RUSH- ~ shy

~ GRASS AREA ) e 0 RI ZONA i NCW )1pound)(1

FIGlJln J-LOClltiOll of thl tnited Htlllcs Hheep Exporiment tltntlou IlQlr J)uhoi~ on tho Snake Jtivor plains of ~ollthcrn Jdnho and the rl1I1RO of I ho Sllgchrllsh~rllSs coor type ill the II Western Htalegt

during the Intc fall und intPI rains arc most common in spring nnd summer During late spring nnd especially through the sumn1(I months rainlpss periods are common during which the soil becomes thoroughly dricd for weeks at a time

In response to the clima~o nncl soil the ycgetntioll on thc stntion rnnge is an unbrokrn grny-hrush formation eovering ahout 25 pereent of the gtound surfn(c in whid1 big sngpbrush (Arfemi8i([ tridellfata) or a closely reIn ted thrcetip sagebrush (A tripartita) Hnd bluebunch wheatgrnss (Agropyron spicatum) nrc dominant Rhruhs constitute more than half of the plant covcr but grasses and weeds make up 86 percent (58 and 28 percent Trspcctinly) of the palatable part of the vegetation of which slightly more than ()l percent is contributed by

2 TECHNlCAL BULLETIN 600 U S DEPT Q AGlUCLl~lUUB

mixture with sagebrush on these lands are highly nutritious andpalatable and what is not then consumed cures well during the drysummers and remains availllble for grazing in the fall The one cropof forage usullUy produced on these ltnds is th(refore suitable for thetwo grazing seasons (pI 1 A) In addition these lands liTe ceutrallylocated between the mountain summer range and valley winter rangeand feed lots and are characterized by a rolling topogrllphy thatsimplifies herding and enables close supervision of tJIC flocks duringthe critical periods of lambing and breedingFrom tho early days of settlement graziers htwc planned theiry6lLrly calendar of operatioIls in accordance with the IIvailn bility offorage today about 2000000 of the 6000000 sllCep thnt grazeannually within the IntelllIo11ntain region nre herded Over the footshyhill lands of southern Idaho during the spring and faU seWOIlS Tilegen~ral pluetice today as in earlier cltt)s is to tU)n sheep on the range

IlS soon as forage become available in the spring hold the flocks therelllltil summer range is f lndy and TetUIll them in the fall to utilizeremaining fOJflgeIn leeenli years iIlereased eompetition for range and tbe reCUllClIceof drought lave 1es1l1 kd in an intensified use of foothillllllds to thedetriment of the J1llIge reSource In an effort to shorten the winterfeeding period and to exclude competing herds from the ltLuge it hasbeeome It common p1lctice for example for operators to commencegrazing tb(ir sheep as soon as )Jant growth starts in tIle spring and toutilize nearly n11 of the forage dlUing the spring period Jeaving littleor none for fall Severe oTergruzing has resulted aod as a conseshyquence extensive areas of spring-fall )Hnge lands art in n seriouslydepleted condition and the possibilities for profitable range sheepproduetion are grelltly dimiIlisbcdClearly if the spring-fall mnge lands of SOlltJ)(jJl Idaho arc to conshytinue to be profituble for range sheep produ(tion the extent to whichthese lttnds call he gmztd without dctlimen tal di(Cts In list he ascershytained and improved systems of manngemellt bllS(( on the knownlimitations IlDd pottntinlities of the forage J(SOllrce put into effectAs It first step in this direetion this Jepolt prcstnts the results ofstudirs (xEuding ov(l the 9-year p(liod 1924-32 Oil the influ(lJ(C ofclimnte and grlLzing on the sagcbrush-wbentgmss range type nt theUnited Stl1t(S She(p Experiment Station The major phases of thesestudies include (1) The inflllenee of dimate more (spcrinlIy t(mshyperature and pleeipitntion on the periods of mnge lise unmwl forageproduction and the productivity of muge sheePi (2) thn effects ofdifferent inttnsitics of spring grazing on fornge production and thenatural rcregetntion of the bunehgrnss unci oti1fl types of forage inthe sngebrusL-wbpatglass 1Iwge type and (3) the development ofprinciples of managpJll(gtJIt based on Tesluts of these studies which itwould be desirahle to apply to spring-fltll range fol the most effectiveconservationanduse of the forage for range sheep production

STUDY AREA

The United States Sheep Experiment Station loeated near thenortheastern extremity of the SIlItke RiYer plains of south(rIl Idaho(fig 1) at an eJevation ranging from 5500 to 6000 fpet covers 28160acres of which 16640 aeres was under fence during the study In

Tedic1 Bulletin (00 l S Dept I Agriculture PLATE 1

EWES AND LAMBS ON SPRtNG-FALL RANGE

t 1))(1 I-ru-OIs HlIel wImiddotId that JU~IW ill luixtllrp ith ~lWfhr[Jsh HilI nOwr -hruhs nrl ftlishlll hy ~Iwtp m Ill ~pnm IHid rallllwi (unslIIUI all itnlorlanl hllk 11 Ii ~armiddotrollht rtI(t supply rqr rnnVll-slt(middotp prOdUlllOtl ill fo(owllllJI fdn~HJ IJ ~htPlf OJI fh~ joflprrathply ~tiltd tx(llriflIl1I1~$tllli()1I raBIH Hlt mllinlHiJwd ill flJlJnS toudUlull Hlld prodWl (Olhlllllly Idlh IUlllh (ropl Hlltl Sithl~ (If wool

3 INFLUENCE OF GHAZING ON SPlUNG-FALL SHm~p HANGE

comparatively recent geologic times a lit fl flow coyered the entire station range and surrounding territory creating a f1nt to gen tly rolling surface on which a sundy loam soil a few inches to seyerl)l feet in depth has deyeloped The nrelt is rrndily accessiblr to linstock but beshycause of the absence of surfnee Wlltrr except where an intermittent stream crosses the northwest corner of the property jt is necessary to haul wnter to the sheep from 11 deCp well at headqunrtrrs

Temperatures nre grIlernlly fnxorahle for plnnt growth from early April untillnte OctohCr Prf1ripitntion rnrrly ex(Ceds 15 inches nnshyllunlly SOlllcwhnt kRR tJltI1l half of the pre(ipitutioll oeems HS snow

-T-~----------------------~ i I i

- t1 0 j

$

bull p---- ---

I I i A )_~ 0 R bull 0 0

amp i i e o~

~ L---~---r- ~ ~~ I ~ - r ~ SAGe8RUSH- ~ shy

~ GRASS AREA ) e 0 RI ZONA i NCW )1pound)(1

FIGlJln J-LOClltiOll of thl tnited Htlllcs Hheep Exporiment tltntlou IlQlr J)uhoi~ on tho Snake Jtivor plains of ~ollthcrn Jdnho and the rl1I1RO of I ho Sllgchrllsh~rllSs coor type ill the II Western Htalegt

during the Intc fall und intPI rains arc most common in spring nnd summer During late spring nnd especially through the sumn1(I months rainlpss periods are common during which the soil becomes thoroughly dricd for weeks at a time

In response to the clima~o nncl soil the ycgetntioll on thc stntion rnnge is an unbrokrn grny-hrush formation eovering ahout 25 pereent of the gtound surfn(c in whid1 big sngpbrush (Arfemi8i([ tridellfata) or a closely reIn ted thrcetip sagebrush (A tripartita) Hnd bluebunch wheatgrnss (Agropyron spicatum) nrc dominant Rhruhs constitute more than half of the plant covcr but grasses and weeds make up 86 percent (58 and 28 percent Trspcctinly) of the palatable part of the vegetation of which slightly more than ()l percent is contributed by

Tedic1 Bulletin (00 l S Dept I Agriculture PLATE 1

EWES AND LAMBS ON SPRtNG-FALL RANGE

t 1))(1 I-ru-OIs HlIel wImiddotId that JU~IW ill luixtllrp ith ~lWfhr[Jsh HilI nOwr -hruhs nrl ftlishlll hy ~Iwtp m Ill ~pnm IHid rallllwi (unslIIUI all itnlorlanl hllk 11 Ii ~armiddotrollht rtI(t supply rqr rnnVll-slt(middotp prOdUlllOtl ill fo(owllllJI fdn~HJ IJ ~htPlf OJI fh~ joflprrathply ~tiltd tx(llriflIl1I1~$tllli()1I raBIH Hlt mllinlHiJwd ill flJlJnS toudUlull Hlld prodWl (Olhlllllly Idlh IUlllh (ropl Hlltl Sithl~ (If wool

3 INFLUENCE OF GHAZING ON SPlUNG-FALL SHm~p HANGE

comparatively recent geologic times a lit fl flow coyered the entire station range and surrounding territory creating a f1nt to gen tly rolling surface on which a sundy loam soil a few inches to seyerl)l feet in depth has deyeloped The nrelt is rrndily accessiblr to linstock but beshycause of the absence of surfnee Wlltrr except where an intermittent stream crosses the northwest corner of the property jt is necessary to haul wnter to the sheep from 11 deCp well at headqunrtrrs

Temperatures nre grIlernlly fnxorahle for plnnt growth from early April untillnte OctohCr Prf1ripitntion rnrrly ex(Ceds 15 inches nnshyllunlly SOlllcwhnt kRR tJltI1l half of the pre(ipitutioll oeems HS snow

-T-~----------------------~ i I i

- t1 0 j

$

bull p---- ---

I I i A )_~ 0 R bull 0 0

amp i i e o~

~ L---~---r- ~ ~~ I ~ - r ~ SAGe8RUSH- ~ shy

~ GRASS AREA ) e 0 RI ZONA i NCW )1pound)(1

FIGlJln J-LOClltiOll of thl tnited Htlllcs Hheep Exporiment tltntlou IlQlr J)uhoi~ on tho Snake Jtivor plains of ~ollthcrn Jdnho and the rl1I1RO of I ho Sllgchrllsh~rllSs coor type ill the II Western Htalegt

during the Intc fall und intPI rains arc most common in spring nnd summer During late spring nnd especially through the sumn1(I months rainlpss periods are common during which the soil becomes thoroughly dricd for weeks at a time

In response to the clima~o nncl soil the ycgetntioll on thc stntion rnnge is an unbrokrn grny-hrush formation eovering ahout 25 pereent of the gtound surfn(c in whid1 big sngpbrush (Arfemi8i([ tridellfata) or a closely reIn ted thrcetip sagebrush (A tripartita) Hnd bluebunch wheatgrnss (Agropyron spicatum) nrc dominant Rhruhs constitute more than half of the plant covcr but grasses and weeds make up 86 percent (58 and 28 percent Trspcctinly) of the palatable part of the vegetation of which slightly more than ()l percent is contributed by

3 INFLUENCE OF GHAZING ON SPlUNG-FALL SHm~p HANGE

comparatively recent geologic times a lit fl flow coyered the entire station range and surrounding territory creating a f1nt to gen tly rolling surface on which a sundy loam soil a few inches to seyerl)l feet in depth has deyeloped The nrelt is rrndily accessiblr to linstock but beshycause of the absence of surfnee Wlltrr except where an intermittent stream crosses the northwest corner of the property jt is necessary to haul wnter to the sheep from 11 deCp well at headqunrtrrs

Temperatures nre grIlernlly fnxorahle for plnnt growth from early April untillnte OctohCr Prf1ripitntion rnrrly ex(Ceds 15 inches nnshyllunlly SOlllcwhnt kRR tJltI1l half of the pre(ipitutioll oeems HS snow

-T-~----------------------~ i I i

- t1 0 j

$

bull p---- ---

I I i A )_~ 0 R bull 0 0

amp i i e o~

~ L---~---r- ~ ~~ I ~ - r ~ SAGe8RUSH- ~ shy

~ GRASS AREA ) e 0 RI ZONA i NCW )1pound)(1

FIGlJln J-LOClltiOll of thl tnited Htlllcs Hheep Exporiment tltntlou IlQlr J)uhoi~ on tho Snake Jtivor plains of ~ollthcrn Jdnho and the rl1I1RO of I ho Sllgchrllsh~rllSs coor type ill the II Western Htalegt

during the Intc fall und intPI rains arc most common in spring nnd summer During late spring nnd especially through the sumn1(I months rainlpss periods are common during which the soil becomes thoroughly dricd for weeks at a time

In response to the clima~o nncl soil the ycgetntioll on thc stntion rnnge is an unbrokrn grny-hrush formation eovering ahout 25 pereent of the gtound surfn(c in whid1 big sngpbrush (Arfemi8i([ tridellfata) or a closely reIn ted thrcetip sagebrush (A tripartita) Hnd bluebunch wheatgrnss (Agropyron spicatum) nrc dominant Rhruhs constitute more than half of the plant covcr but grasses and weeds make up 86 percent (58 and 28 percent Trspcctinly) of the palatable part of the vegetation of which slightly more than ()l percent is contributed by

---

4 TECHNICAL 13ULLI~TJX GOO V -i J)J~PT OJo AlflUCULTUHE

three species-bluebunch whelltgmss bluegrass (Poa secunda) and balsamroot (Balsamorhiza sagUtafa) as shown in table 1

TABLE l-Total plant cover and prevalence of palatable forage on 100 sample plol3 of spring and fall middotrangc at the U S Sheep Experiment Stalion by species

ToLnl plan L covcr Esti lulutublc lorago lIlated

Species relnthmiddotu pulntamiddot

Detlsily Compo~ bility 01 In tolul Compomiddotsilion covor si Liollspccics

I I

Shrubs Perce1lt -- - -- Sagobrush (Aremiia rillarifa) 10 ~IH 10 I I 07 03 Yellow brush (ChryolllUlI7IJ81l1lbcTIIllts) 1 51f 550 20 I 10 15 Blttorbrush (Pllrshiaridelllfltfl) - 1127 middot100 21 102 33 lIorsebrush (7cmdymirtcflllesCfn) bull _ I 09g [102 5 IR n Olhers - I(jl JO aa 20 bull r

bull ___0 _~ ____ bull ___

TotuL _ __ 140Bo 5121 --147--14 3shy==~~--Grassos

BluobullCh wheatgrnss (AgrollvrOn lliro1I1II) bull 4228 15H 71 IIW J08Bluegrass (Poa seC1ndo) bull 1(108 166 00 ~ 2H 1OnJuncgrass (Koeleriu cristolrt) _ roO 185 70 1 211 4 IBigmiddotsplked whcntgrnss (AgrOllyrOll dOV8tlchVIl1U)middot middot14 157 fO 25middot i8Necdlegrass (Stilla comalo) _ __ 200 108 70 middot in 2 Hicegrass (Oryzollsis hymelllliilc) bull 121 44 65 29 9Others__ __ bullbullbull __ bullbull __ __ bullbullbull __ bullbullbullbull IIlI 60 20 middot 14 5--- __ ~~--

TotnL __ __ __ _ 67110 24 oJ ~

-~--

--- 180middot 57 i ======

Wec~ IBalsntltrDot (Bala11l0rhiza ogillalo) bull __ bullbullbull 29110 1088 40 4 ali la I Lupin~ poundlIll i1lU calldallls) _ 7U8 200 40 116 37 IndiunmiddotLo~acco (Eriogolllull spp) bullbullbull __ bulla5 I 28 20 26 8 Pussytoes (Antmllaria 1Uicrophyllo) __ 115 11-1 15 17 5 Hawksbcard(Crcpi8aC1Lmi1lata) ~ lto~~c~_r~_~ 215 i8 no ~70 2 lhlox Phlox 1IIlLltiJlora) _ _ 212 77 85 65 2 I Aster (Ater spp) _ __ ]08 72 25 18 6 1oco (AIragaI1l8spp) - bullbull _ __ bullbull 181 61i tiO 40 13 Snakeweed (Gntierrezia orothrae _ _ 1middot17 51 10 05 2 Stickweed (Lollpilia occiilealali) 116 42 5 02 bull I Others 572 2(18 40 82 26

TotuL __ __ omiddoti06middot1-22161~~rR77-j-28~O Total IIl1s11ccies _ _ bulli~~=~~(=~=gr==wooo

The range forage makes its maximum growth in the spring niter temperatures rise to a level fnvorable for plant growth and when moisshyture from the accumulnted winter snows js availnble Ordinarily the grasp-es and weeds start growth early in April and complete growth befoleJuly 1 after which they remain dormant during the dry summer In some years suificient prec~pitation occurs in the fn11 to induce reshygrowth of grasses) but even m favorable yenrs the volume of forage produced as regrowth is negligible The grasses that complete their growth in the spring cure well during the summer however and when moistened by the fall rains they are readily grazed by sheep

The experiment station maintains about 2500 sheep including Rambouillet Corrie-dille and Columbill breeds These are selected and bred to develop qualities of thriftiness by which they will make the most profitable use of the native forage under the prevailing cirshycumstances of climate topography and essential methods of hanshydling (1) 3 (pI 1 B) The aim of management on the station range as a whole has been to provide through a conservative rate of stocking ample forage for the sheep in the spring and fall seasons

bull Italic numbers in parenthescs rcler to Literature Cited p 42

INFLUENGE OJ GRAZING ON SPRING-FALL SHEEP RANGE 5

METHODS OF STUDY

Five 80-acre paddocks were made available by the Sheep Experishyment Station for purposes of this study These were located wIthin a short distance of the station headquarters and were fairly similar with respect to plant cover topography and soil to the herded portion of the station range already described Because of differences in the amount of palatable forage however the grazing value of the paddocks differed somewhat at the beginning of the study As shown later in tables 9 12 15 18 and 21 the estimated average total forageproducshytion per paddock during the first 2 years of the test period ranged from 8125 to 6525 sheep-days per acre or a diflerence of about 18 percent between the best and poorest areas which was considered of minor importunce in this study On these paddocks intensive use of the forage was instituted during the yeurs 1924 to 1932 inclusive approximating the systems of use commonly appliecl in private operashytions on comparable lt1I1ge lands in the vicinity of the station A different system was applied to each paddock These muy be eA-plained briefly as follows

A RenNY continuous spring aLd late fall grazing (paddock 2) In this paddock an average of about 68 percent of the forage was removed during approximately a 2-month period in the spring after grasses reached 2 inches in height 25 percent wus taken in the fall making a total of 93 percent for the year This system is representashytive of practices on extensive range areas where one or several bands of sheep gmze more or less continuously throughout the spring period and utilize neurly all of the forage at that time only to return and regraze the area in the full

B Heavy early spring and late fall grazing (paddock 3) On this area an average of about 36 percent of the forage was taken during approximately a 4-week period in the spring commeneing I1fter grasses reached 2-inch height growth and about 46 pereent was removed in the fall This system is typical of 1lse 011 arens where sbeep are turned out to graze ubout the sume time eaell spring but beeuuse of avltilable range elsewhcre the lad of water or other reasons the use is limited to an early short period in the spring followed by more complete utilization in the fnLl

C Heavy lnte spring and late fall grazing (paddod 8) This pasture was grnzecl mtch year so as to utilize about 53 pereent of the forage in the spring within the avernge of approximately a 3-week period after grnsses ]Caehed a 6-inch height growth and 37 pcreent in the fall This arrangement conesponds to situations where sheep relleh the rangc and consume about hnlf of the current growth after the forage hns attained advanced stnges of development and where the same rnnge is subjected to close fall gmzing

D Moc1ernte lute spring and heavy fall grazing (puddoek 7) Gra7ing on this arca removed during npproximately 3 weeks in the spring all a velnge of 19 percent of the forage ufter grnsses reached 6-inch height growth while in the fall 66 percent was removed This system diflers fIOlll that followed on paddock 8 in that spring grazing was confined to a shorter period und was less heavy It is characshyteristic of the maI1ner in which some ranges nre grazed rather lightly in the spring after which they are heavily utilized in the fall

6 TECHNICAL 1llLLEJJX 600 U ~ DEPT OJ AGHIOULTLTln~

E Heavy fall grazing only (paddock 1) As check on the other systems tlLis paddock WfiS grazed only late in tbe fall forage COllsumpshytion averaging approximately 83 percent

The paddocks were grazed in the spring by ewes nnd young lambs while in the fall only mature ewes were admitted except for a few rams during part of the time for breeding 1he numbers usually grazed in each area from day to dny varied from 30 to 40 head alshythough for a few days at u time it was found necessnry to decrease the numbers to 10 or less wIlen sheep were not available 01 to illcrense the numbers to 100 or mOle in order to mop up rernainillg feed The sheep were of the same classes that wele grnzed on the Jllnin portion of the station ra nge the Pllc1docks however were grnzed without herding while Oil the stn tion range the bands wore undor the CUTe of sheph(rds Since the Jlumbll of she(p-dnys of food JWl aCIc obtalJleclullcl(l pnst-ule glozing mny llOt be compnrable to the number obtained und(~r herded conditions the dnys of flNI )(I ftCI(~ flOIn the paddocks have not b((n taken us nn indicntioll 01 cnTTin cnpaeity for herded Jitnglt but hnvo been lSpel simply m all illdpx of range productivi ty

Detniled reconls WPIl kepI of the uLlInb of sLo(k admitted to each pnddoek ns well ns to the JWdCcl rnngC and )1 the J1llInbl1 of days tlwY Wlre glnzed in the spring and full At Ute close of the fn1 seasoll the gross consllrnptioll wus cstimated clumps tnlwll to within 1 inch of the ground h(ing (onsidcJod 100-pltlcont grHzed The extent to wlll(h glasS(IS wero eoppecl nt tlll~ end of the seuson wus tak(11 ns n eonvpnient and fnirly reliable index of the total quanshytity of forage eOllsurned For ench yenr the Sllm of this nmOUll~ aelded to the remaining glflss-expnssNl in sheep-clays of feedshywus tnken as the totn1 qunntity of JOt1go plodueot4 Jt WIIS lenlized from the outSlt thllt n direct nnd n((UInto measure of utilizutioll of all (lassos of fOlflge wns c1nsirahle for this study sinee obsClvntiolls indicate thnt sheer) consume considelnble quuntitios of weed fONI during the spring when grnsses nle nynilablo nnd inclNLsing amounts of sngpbllsh foliage in the fnll ns the gllSS feed boeomes exhausted GrnsFes not only constitute the mnjor pOIlion of tllll fomge PJop on this Tange but aJl the only plnnts of whic-It tIl( ufilizulioll ClUl he rendily JllcnsuJec1

1he Tesponse of the JUlIgc cOV(r to the influence o( dimn tc nnd grnzing was determined hom plnnt-deyploprnpnti records plnnt inventories and measured qUiLdInts The plnnt-d(yplopnwnl rocolrls included ohservntions of the time wl1(11 the grl1s(s as the principnl fornge plnnts stnrtpd growth cHeh yenr and renehed 2- 4- und 6-inch height growth seed fOlrnntionnnd the sturt of eming Au iwentory of the vegcta tion in the pnddoc ks Wl1s mude by runge r(eoJUmiSSl1Ilee 5 in 1924 l1Ild again ill 1930 to detellnine the trends in the density and composition of the vegetntion The h(hnviol of the grnses WllS

observed more eliticnlJy in the yenrs 1923 1926 1927 1929 1930 1931 and 1932 on flmetcr-squllre qunclmtin each of thcfiw pnddoeks

bull 1ho I)middotyeur Ilerugo estimuted 10Llll fomgo production wns derived simillirly using the I-yollr nvorngcs of yearly totnl use ofrnngo und lertCnt fonl~e USOrillS II iJIISO rho pOrLCnl of f()ra~o lIsed in tho sprinl( und ful each Yfur wus derived froUl 1 te rntins of the SIWl(Hlnys tlor R(Te uso of tho range in the SIJring and fnll rospeCa t1velv to tho ostlmuted 101111 forugo prodlHti()n fur thilt Ylur Rimilllril tho 1YllIr nerugo perttnts ()f foruge used in tho spring nnd fill wero derivod frum tho rutios of tho lImiddotyoir uVenlge shOOIHIIIIS per nere uso ofrnnge in tho sllring Dud (nIl resp~GtheIY to lhe cHlculutod Umiddotycnr nerH~o ostimutcd tntu fonilo prociuetion

Made in nccordanco with Instructions for Umzlng Sunoyg Oil NnLional ore~ts mimoogrnphed report of the Joorest Sonlco I L relsed In 11135

6 TECHNICAL 1llLLEJJX 600 U ~ DEPT OJ AGHIOULTLTln~

E Heavy fall grazing only (paddock 1) As check on the other systems tlLis paddock WfiS grazed only late in tbe fall forage COllsumpshytion averaging approximately 83 percent

The paddocks were grazed in the spring by ewes nnd young lambs while in the fall only mature ewes were admitted except for a few rams during part of the time for breeding 1he numbers usually grazed in each area from day to dny varied from 30 to 40 head alshythough for a few days at u time it was found necessnry to decrease the numbers to 10 or less wIlen sheep were not available 01 to illcrense the numbers to 100 or mOle in order to mop up rernainillg feed The sheep were of the same classes that wele grnzed on the Jllnin portion of the station ra nge the Pllc1docks however were grnzed without herding while Oil the stn tion range the bands wore undor the CUTe of sheph(rds Since the Jlumbll of she(p-dnys of food JWl aCIc obtalJleclullcl(l pnst-ule glozing mny llOt be compnrable to the number obtained und(~r herded conditions the dnys of flNI )(I ftCI(~ flOIn the paddocks have not b((n taken us nn indicntioll 01 cnTTin cnpaeity for herded Jitnglt but hnvo been lSpel simply m all illdpx of range productivi ty

Detniled reconls WPIl kepI of the uLlInb of sLo(k admitted to each pnddoek ns well ns to the JWdCcl rnngC and )1 the J1llInbl1 of days tlwY Wlre glnzed in the spring and full At Ute close of the fn1 seasoll the gross consllrnptioll wus cstimated clumps tnlwll to within 1 inch of the ground h(ing (onsidcJod 100-pltlcont grHzed The extent to wlll(h glasS(IS wero eoppecl nt tlll~ end of the seuson wus tak(11 ns n eonvpnient and fnirly reliable index of the total quanshytity of forage eOllsurned For ench yenr the Sllm of this nmOUll~ aelded to the remaining glflss-expnssNl in sheep-clays of feedshywus tnken as the totn1 qunntity of JOt1go plodueot4 Jt WIIS lenlized from the outSlt thllt n direct nnd n((UInto measure of utilizutioll of all (lassos of fOlflge wns c1nsirahle for this study sinee obsClvntiolls indicate thnt sheer) consume considelnble quuntitios of weed fONI during the spring when grnsses nle nynilablo nnd inclNLsing amounts of sngpbllsh foliage in the fnll ns the gllSS feed boeomes exhausted GrnsFes not only constitute the mnjor pOIlion of tllll fomge PJop on this Tange but aJl the only plnnts of whic-It tIl( ufilizulioll ClUl he rendily JllcnsuJec1

1he Tesponse of the JUlIgc cOV(r to the influence o( dimn tc nnd grnzing was determined hom plnnt-deyploprnpnti records plnnt inventories and measured qUiLdInts The plnnt-d(yplopnwnl rocolrls included ohservntions of the time wl1(11 the grl1s(s as the principnl fornge plnnts stnrtpd growth cHeh yenr and renehed 2- 4- und 6-inch height growth seed fOlrnntionnnd the sturt of eming Au iwentory of the vegcta tion in the pnddoc ks Wl1s mude by runge r(eoJUmiSSl1Ilee 5 in 1924 l1Ild again ill 1930 to detellnine the trends in the density and composition of the vegetntion The h(hnviol of the grnses WllS

observed more eliticnlJy in the yenrs 1923 1926 1927 1929 1930 1931 and 1932 on flmetcr-squllre qunclmtin each of thcfiw pnddoeks

bull 1ho I)middotyeur Ilerugo estimuted 10Llll fomgo production wns derived simillirly using the I-yollr nvorngcs of yearly totnl use ofrnngo und lertCnt fonl~e USOrillS II iJIISO rho pOrLCnl of f()ra~o lIsed in tho sprinl( und ful each Yfur wus derived froUl 1 te rntins of the SIWl(Hlnys tlor R(Te uso of tho range in the SIJring and fnll rospeCa t1velv to tho ostlmuted 101111 forugo prodlHti()n fur thilt Ylur Rimilllril tho 1YllIr nerugo perttnts ()f foruge used in tho spring nnd fill wero derivod frum tho rutios of tho lImiddotyoir uVenlge shOOIHIIIIS per nere uso ofrnnge in tho sllring Dud (nIl resp~GtheIY to lhe cHlculutod Umiddotycnr nerH~o ostimutcd tntu fonilo prociuetion

Made in nccordanco with Instructions for Umzlng Sunoyg Oil NnLional ore~ts mimoogrnphed report of the Joorest Sonlco I L relsed In 11135

7 IN1LUJ~NCB Ol GUAZING ON SPRING-FALL SHEEP ltAGB

and on two quadmts in each of two small fenced areas from which grazing WilS excluded

In connection with the concurrent breeding sludies being conducted by the Bureau of Animal Industry individual records of weights losses and production were mailltuined for all animals Although no special group of unimals was used in the grnzing tests records were made available for determinhlg the influence of mngo conditions from year to yeur on body weights of mature ewes in the spring and fan weights of fleeces at sheming llumher of lambs horn and weight of lambs at birth and wenning

Since JallUitry I 1924 records of maximum and minimum tempNshyatures and precipitation have been lluLde daily in the vicinity of the sheep station headquultels Precipitation records were also avuilable at Idaho Falls for the 27-yenr period 190G--S~ and at Boise for the 60-year period 1873-1982 Although these latter stntio~lS nre situated at distunees of ahout 50 mIles south nnd about 200 mIles southwest respectiYely of tbe stution range the Tecolds tlrc fuilly compllrable and nre jndieutive of the eliml1te which prevailed over the Snake RiYer plnim )Iior tO ftnd d llring the pctiod of study

CLIMA1IC INFLUENCES

Climatc with its bnffiing uncertninties is generally recognized as one of the most importnllt single influences alfeeting range sheep production on the spling-fnlllange lands It influenceR the period of growth as well us the qUlLlltity of iOlnge produced These in turn afrect the period of use of the range and the number of fihecp-dnys of feeel prod ueed ench year Heretofore on spring-fn II rnnge these influences hnye for the most part been dt terll1ined only in general terms In the present study definite meltSlllements were mnde of the exten t to which periods of lflnge tlS( annuu I folngc plOd Hction Ilnd the ihliftineRs of mngo sheep Me nfreded by preltipitatioll and tempcJntllle

CLIMATI~ DUiUN(J THE 11~1tI0() OF STIJI)Y

Temperntulcs ns summarized in ttLble 2 indicate a 7 -month growing SeltSOll extending ill most yeltlS from April through October with the lowest mean monthly tempemture in Janunry nnd the highest in July 11enn monthly temperature dropped below 40deg P in October 1928 al though jn all other years the meUIl for this mOil th exceeded 40deg It continued especially low in the enrly spring of 1929 the meall for April hnying been only 3155deg ns compaTed to 4987deg in ] 930 and the uvelage of 4238deg for the 9-yenr period Low daily tcmpemtures were recorded even into curly summCJ nnd ngain in eitJly full Frost ocshycUlreu in nll months of eitch yenr except July and August Because of this wide rnnge of daily temperatures toe time nt which mean temshyperntuJes rOse to 40deg in the spring or fell below this level in the aushytumn delimiting the flLVo(nble growing season varied widely from yelLl to yenr In geneml hoover it may be snid tlmt daily mean tempeJl1tures rernl1ined above 40deg from April J0 to October 20 COIlshystituting all uyemge period geoell111y fltvomble for plant growth of J93 days This mlty be ueeepted us the ureruge growing perioo for this Jo(nJity but it must be kept in mind at the same time that temshy

8 tECHNICAL BULLETIN 600 U S DEPT oJi AGntcULTURE

perl)tures within this period are subject to occasional wide fluctuations which may also hl1ye 1111 important hearing on the growth developshyment and use of the mnge forage

TABL) 2-11ean mOlthly lem ]lerat nre~ at the United Stutes Sheep EX1Jerilllent Station 1924-82

Year June July~~yl ~~~ M~~Ch -~~r~~I MUy ~I~i11 fe~~- ~~~t ~31 e~~ o ~ ber ber ber

---------__- --- ----- -----shy01middot 0 F 0 P 0 Ji 0 0 P 0 i 0 F 0 Ji lo3O~1 0 N Q f

1924bullbullbull__ bullbullbull_bullbull 1947 28 fiG 28 i2 424 0105 OiOO 083i 6714 45 II 3011 14 i9 J92~L__ 21 48 ~I 05 8248 4H88 55 If M55 Oi73 G320 5535 4448 ll la 2071 1926____ bullbull __ bullbull 1II47 2808 3558 middot1018 5281 02W 0552 6205 4718 579 l4UO 2106 1U27__ bullbull__ 2051 ~l8U 3081 4123 4i87 0108 0910 0443 gt547 4700 3045 1770 lU2~Lbullbull __ 2108 247middot1 15351 mil 570215630 0941 0408 50o Ii 32 3172 ISOO 19211 1190 14110 2150 155 4679 M88 flO OS lIl it 4918 42 i4 2410 2551 JY30 JJIO 2807 1108 49bull 1i7 5208 WflO 7224 6i85 5i20 middot12(J( 28G5 1695 1931 __ 2012 2middot1 14 2720 middot130 rrOO M78 i810 0880 6280 4070 2S80 2000 1132 __ __ 11S0 118iO 2400 40~0 5200 j 5900 0000 6685 5U20 41iJ 3349 1140

1 A ()rage bullbull -i7Sul-~iW io2u- 238~ imiddot[3 52Tiiil3oI09300582T-Z2-j4359 il--I-m~s

_____1__ t ___~ ____-___1 ~

PHECI PtrlAJION

Precipitntion nveraged 1018 jnches foT the seasonal year (Oct 1 to Sept 30) during tJw period J924-32 (table 3) On the average 438 inches fell as snow and ruin during the 6-month period October 1 to 1farch 31 and 580 inches principally as min during the spring and summer montJJs The llemge fall however varied widely from yeur to yeur from month to month in the same year and between the same months in cliflelont years

TJml~ 3-Monlhly ~ea8on(l lind annual 7Jreci1Jitaiion recorcled lit the United Stales Sheep BJ[lerilllfut Stalion October 1928 to September 1[M iHclu~11e I

~I Olllh- --------- HI2~J~ 2~11125-21020-2 1~27_2)HI2R20li 1021~IOIaO-J1 1931-1~~~~ I I I t age

I i -----i--i~I---t---i-middotI------

Octoblr I __ __ bull __ bull __ bull __ I Jllchr Illcu IIIClt ll1Cht Illche j Illches Illches I Illches Ilches IlIche2middot10 I 3M II~ 012130 U53 071 233 014 11l

Noyclllb(r ~~ 41 4n 131 59 01 Ii 125 iO 69December _ bull j() 112 115 US 05 72 middot15 17 246 87January bullbullbull ___ _ 1 25 (H JjJ bull ~a 21 bull -15 a2 t bull tlf 78 fi71lt(bruary _ 100110 middotIH fl5 96 ~I 49 7030 sallnrch ~ 1-1 JO O~ 3i 10 87 10 50 23 bull ~3 ~ 1 70 bull (i0 41 21 1 gi 9 0-1 87 7~ pri bullbull __ _ ______ bull__ bull ___

l1n~middot_ __ bullbull _ I 120 bull4(J 1 2[0 1 10 53 144 I Oil 74 104June __ bull li7 196 n 02 L[5 Il 100 I JO 2 I 109 J3 89 10 lS 70 01 211 07 252 bull ill ~~~~lC o 2 Ii bull 4 bull 78 bull 15 65 2 g bull OS 1 29 I 08

Septelllberbullbullbull I 70 20 bull W I I fI bull fi5 bull~7 201 I 82 bull U I 10

12middotmonlh total _bull os ~~- In 111 -1ioOTiO3U -01 iO~iiJ -lD 79 8ii -1227--Qj8 = ~~=--=~=~- l-_=~

Wintlr period (OcL Ilo llnr (I 185 37tj 2fi5s~~I~iiimiddotmiddotlierjO(rmiddot(rlirmiddotllo I 140 535 4 in middot118

Jnnc30L __ bull sa 4 U2 IOD 102 280 174 3 Ii j40 305 280SUtflllllr fllriod (Jul)- J IQ

Sept 10) __ e- I 201 b (13 100 2 iI 100 250 484 217 3 SI 294

I nccnll~p It (()lIrorlll~ lI1or~ lllllrl) to the Ind or the perioll when tempIfIlUmS an faorable to plant growthlharecorll htls IleC com (l1I(d for tl 1i-month Plrlod CUlling Sept 30 ratlllr thnnlhe nglllnr calendar year

lho IIIhws for Octob(~r XoVmber 0111 Dcemblr of the cnlll(lnr Ylnr 1921 herein listed us the first 3lllonth~ or lhl s(usOlml Y(llr Hj2I-~middotI were derived rrolll records 1 8 stations withinlhe Snake lUler plains section hallng esslntllllly tllf slime (harnetr nnit 1lll1OIInt or Pflclpitntion as at thl) Sheep ~xJlerimentStation

9 INFLUENCg OF GRAZ1NG ON RPRIG-ImiddotALfJ ~Hggp RAXGI

According to the records at the experiment station ] 925 IUld 1932 were the only 2 yelus in which precipitation WitS distinetly above average while 1924 1920 1928 and 193t were considell1bly helow average That prcripitntioll may have becI1 generally more deIicient than is indicated by this short record is suggested by the longer record of precipitntion at Idnho Fnlls For example as is shown in table 4 the average annultl precipitation at Idaho Falls during the period 1924-32 was 975 inches as compared to 1018 inches for the same period at the experiment stationa The 27-year record nt Idaho Falls however shows that 1102 inches is more nearly llormal iLnlluaL precipitation for that locality suggesting that the 9-year period 1924-32 was about 10 percent below nvernge Aecording to this relationship and in view of the similarity 01 the climate nt thltse two stntions more nearly nOlml1 precipitl1tion Itt the expcrimltnt stntion should be about 1215 inches instead of the 1018 inches rceorded On this basis it is not unrel1sonuble to nssume that ] 921j wns the only distinctly wet yenr at the experiment station during the pcriod of study all other years except 1932 huving been considerably below normal

TAIlIgt 4-Annual prcci])itaUon at idaho Palls (Oct 1 to cpl SO) 1l()6-82 ---middot--1 pnmiddotIT - Pn d I pn-j----- --rshyYnr cfpllamiddot 1 Y~nr 1 cipitI i Ypur clpllnmiddot AIcruga clpltnmiddot

Iion 1 i lion Ii lion jillion _____11 11

IIKJ6

i Inf~~~8Ii HIlIi bullbullbullbullbullbullbullbullbullbullbull lnrgrgi Ig24---~-Imiddot 11lcirtl1127_~I~j-1007 - nOI lOW 1000 lJ25 bullbull __ bullbullbullbullbullbull J2[oO II ngo(lOOtI-32) 1I02 1008 _ 1304 1017_ bullbullbullbullbull __ 1I17 1120 i5B 10yearnnrngc 11lOl bull __ _ 144211018 10(17 lim 1048 I (1021middot32) 075 1910 bullbullbullbullbullbullbullbullbullbull 7 it IlJO 8 J I 11128 _ 877 II lOmiddotycnr IIImiddotcrmiddot 1011 125 1920 1141 I 1O~)IL_ J2111 l II~ (1000middot15) 1402 1012 1080 I Hl21 JU5j 1930 __ bullbullbullbullbullbullbull 8SSIIIi)middotcllr lllmiddotcrmiddot 1913 lil3 1 1022 905 I Hlal 821 il IIge (1910-32) nBtl 1914middot middot1 14111 111921 bullbullbullbullbullbullbullbullbull 830r 1Ol2 1302 j

Further I1l1alysis of the records nt Idnho Fnlls us preS(ll ted in figure 2 shows that precipitation wns distinctly below normal not only during the 9-yenl period in which the studilts were eonducted nt the experiment station but for a period beginning as early ns 1916 For example nlthough the menn anl1unl precipitation Jor the lO-yenr period 1906-15 Wl1S about 26 percent more than the long-time nvell1ge with only 1 yeur of drought~ the I7-yenr period 1916-32 was in all but 3 yel1Is considell1bly below tLyerage The melLIl 101 the 111tter period was l1bout 15 percent less than the long-time average

Further cyidence oJ the severity of the drought in recent years nnd the probahility of recuning periods of dry yeurs (1111 be deduced from precipitation reeords at Boise for the 60-yen1 period 1873-1932 (fig 3) dUTing which nil ultcmute scrics of wet and dry yenrs vcry much resembled the shortcr cycle shown in Jigure 2 except that the drought thut began in 1916 at Idaho Fulis did not start ut Boise until 1918 The reconl Ht Boise also shows thnt eompllmble eyeles occurred prior to 1905 but they were inegultLr in duration l1ud not neurly so long as the most reeent drought It uppeUTS obvious thnt periods of

The sll~htl~ hi~h(r pncipitlllion on the shc~fl stullon rungc llnlollbtculy Is IIccuuntcd for by its closer proximity to tho (onLincntul Divide

17fllll -18-2

10 TECHNICAL BUU~I~TJN 600 U S DEPT 01 AGItlUUIJrUng

IO-YEAR AVERAGE= 1462

~-----~------~bull A

J

V1 27-YEAR AVERAGE=I162~

I I --- ---- ~

A I - o --~-~ _ -r

A ~

----- _-shy I ~ shy

Jv _ V --- ---- - shy-~- ----_ --- shy

- -17-YEAR AVERAGE = 986

I r 1910 1915 1920 1925 190

FIGURE 2-IhQ departures Irnlllnurllllli prerlpituliol1 III hho Fnlls JOOIHI2 showing u COI1eelllr~ti()n of surplus lIIolsture during the period llXHf lind 1111 nc(ulllullltiOIl of lIIolsture dchmiddoticuclI during the penoel lJlG-32o

8 - 5-YEAR AVERAGE=1557 I 7 ~~5-YEAR AVERIGE __ 13-YEAR AV~RAGE

~ 2-YEAR AVERAGE ---I-----Ic- shy~ I =~ ~ =1693

~ -_K ~ -- --- --j-----t-f-I---+-----j------j

~ 3-- -1--1-middot-I--I---I-+-+----H--middotmiddot--j----1----1 ~ r-- I

2-- - -i-- -- middot--4-+=-I-----fc-l-----i------+-----1 l5 Ashyi 1--- -~-ilr -- _ A -r-- rc1=~=4Lr-Ilr~I~-~_tI-_-t+--f---_-_-_--1-1

~ ~ IJjjJI VI il ILYJ V - t-j ____

~ 2f-----j-middot - - ----- nJ-=V --~ ----j ~ 3~---__----Ij 1-------1middot1-l---~-----IH---l ----l I-----~ tl 4 -C = - ~ 5-YEAR AVER1AGE 5-YEAR AVERAGE 0 Sr-- =1230 -IO-YEAR AV~RAGE - =1127 Isect 6 L=1212

k-------d-----f------------t--13--Y~R AV ER AGE = 1177 1870 I~BO 1690 1900 1910 I~O 1930

FIGURE 3-DcpllrtlIrcs from the normlll prerlpltlltlon nt Boise Itlllho durinl the G()~enr period J873-JIII~ showing the Irregulnrly cyclic trends oC wct und dry YClirs

drought ll1Hy be expeeted every few years in this locnlitv lind tlllttsomo of the periods during which moisture is defieient mny oil the average be extended ovcr ns mnny ns 17 ycnrs

INFIUENmJ OF CUMAn ON GnAZING lEIUODS

The stnrt of plant growth in the spring lim the rate ut whieh the forage develops nre of grent im portnnce to the users of spring-fall range sinee they determine the 1Yllilnbility of succulent fornge ILt thllt time of yenr nnd fix the dnte when spring gmzing (un begin Moreshyover the length of time during wliieh the fornge remnins green in the spring Inrgely controls the dllrntioll of the spring glUzing period Simshyilmly the lcnifth 0 r tho fall grnzin~ period 11ingcs lurgely on tho tLmoun t of fced tlllt IS crt nftel tho spllng period tho nmollnt of regrowth which O((IlS in the fnn nnd the OCCUlrOlWCl of dcep SIlOWA

Detailed observtLtions of tho growth stug(s of hlu(blllleh whentshygruss HS stlmHlnTizelti in tnble 5 TClvenl thnt this plnn t started growth on tho stntionrnnge ns eurly ItS llnreh 20 und ItS late us Aprii24 Twoshyineh height growth on the IW(lnge wus nttnillld 011 April 22 but onee us Inte as l1ny 1 FOllJ- nnd sixIllCh stageA of growth were rCfwhed in 1 yenr us eHlly m April 21 nllltl 2(j respectively ILlld in another yelL] ns lnte ns l1uy 16 lind Tllne 1 Spcd wns fOTJ11ed before June 10 in 5 difler(nt yrurs and (~tlJing stnrtcd nt diHcren t clLtes betwetll June 11 nnd August 5 All thesc growth pcriods vnried widrly from yeur to yenr in thpil dlLteR of oreurrence

TAllI1l i--bullJ chroll(ficlll 7ccorrZ 0 Ihl) Inoes of olowih of bllcb1llch whcnl(lTns8 (A (I0Jlllron 87ricalum) UJ2S-Sd

Iorossmiddot oross (lrnss Orl~ss Kmiddotmiddot (urin

Y(ar slllrl~r1 2 1I(h~s 1 In(lws (I 1lIgllltrs rOTIIlti I slnr(~dgrowth high high I

~o~---middot~~- - ~ I~- 1- r Iune ue-~r- 1024 bull bull pr 7Apr2a lIlay 71 1 tint I JUlie II 1025 Apr 2 Apr Jj Apr 3n Mar r IMW 2() llJlr 10 W2(1 Apr I Apr HI Apr 21 Apr20 lr 12 Juno JI tn2i Apr 21 lIIIIY I lIIIIY 17 MIlY 25 UlIO 15 JUliO It) 1925 1I111r20 Apr 27 1Iiny G Mny 10 Iny ~i Jul) 25 1020 bull bull Apr 14 Apr au 1Iiny 111 I llay IR I IUlI( 21 July 21 1130 bull bull pr J I Apr 15 Apr 22 I ilIIIY fgt I June 20 JUliO 25 1U1l bullbull bullbullbull do IApr IS Apr ao 11I1IIY I(J I IIJII(I 15 1032i~p~~~J~~~ ny I~ IUI~~_5

Alwag 1 Apr 61 Apr 22 11111) 4lIray la I JUlIll 8 July 2

1- f)Y~I- ])(11 I J)uyx i-J)~(-)v =])nv Hnngc or dnl~s i 36 IS i 2 i 17 no 1 fin

The dut(s on whieh plan t growth sturted were espOlially vllrinhle the rnnge in the 2 yenrs Hl27 nnd 1928 being 16 duys On the other hand the elllliest nndlutcst ltintrs on which 2-illeh height wus renehed never exeeeded a mnge of 18 dnys Since soil moisture oldinnrily is plentiful 101 n period of nt least 2 wc(ks following the melting of SIlOW the primflry relson for the glCILt diffcrenee in runge between tho start and Gompletion 01 the first stnge of growth nppcurs to be due to temperatUle fhat there is It close rclntionship bctween theel1r]y development of this gruss nnd the rise or temperatures is jlldicnted in figuro 4 Here it CUll be seoll that the nvemge lLnd runge of dntl~s 011 which the stnrt of growth and 2-illch development occulTed nellrly

12 mCHNlOAIJ HUrJ WrlN 600 U S D1Hl 01- AiJHICULTUIH

coincide with the averttge HJl(1 the loweRti lind highest JTilltII monthly temperatures

Later stages of development inrluding 4- and 6-iueh stl1ges of height growth seed forml1tion and curing 111so vnried widely because in oddition to the varying tempemtl1les to which the plants were subshyjected moisture became inereusingly uncertain as the sensons proshygressed The combined eCleet of tempernture and plecipitn tion on pll1nt development is illustll1ted in the growth record of the blueshybunch wheatgrass under the difleren t (onditions prmiddotevniling in the 2 yel1rs 1930 and Blal (fig 5)

In these 2 years growth stnrted tiL the heginning of April tilightly higher tempeiutlllles prtyuiled during M1I1t month in Hl30 than in 1931

I =IO-Y~AR AV~RAG~

r START OF CURING I9 0 5p DAIS

SEED FORMED80shy 60 DAYS

6 H~IGHT 0 37DAIS1 ~

~ ~~-~---

1) 4 HEIGHT ~ ~

0 27 [lIIS 14~r

HIGHEST MONTHLY - I MEANS RECORD~ ~~I-IJ

I ZHT 0 7V

-J

~LOWEST MONTHLY MEANS RECORDED

START OF GROWTH I 36 DAYS i I

-I---

3 0

0

10 20 10 20 10 20 10 20 10 20 10 20 MARCH APRIL MAY JUNE JULY AUGUST

OURE 1-A crngc lind range In dales on Ihleh bluehunch whcntgrnss rcnche(1 ImporlJlnt strgcs of developmcnt In relution Lo IIvcrngc nnd lowcst nnd highest menn mO1thly lcmperntures rccorded 1D24-32

Moreover rains occlIlTed in each 10-d11Y intervnl in 1930 whelCl1s only one light shower occurred toward the end of the month in 1931 As a Tesult early forage growth WitS tho more lnpid in 1930

A substantial rain el1rly in 1vIny 1930 contributed mnterinlly towllrd the maintenance of Ilclequnte moisture for thnt month but 11 lowering of temperatures occnsioned hy the storm tended to curh fornge developshyment Although tempernturcs were higher in 1931 n continued lack of moisture held plant glowth in check until nel11 the end of the month As a consequence the net growth of forage in both years up to June 1 wus nbout the sume with the importunt cxeeption that in 1930 the grusses quickly attained 11 height growth suflicient for grazing wherens feed wus short during most of Muy 1931

INFLUlmCl~ OF OHAZING ON SPRTN(1-JALL SHEgp HANGJ~ 13

Late in Mny 1931 a heavy shower oceurred which completely altered plant growth in June of that year as compared to the same month in 1930 when only light Rhovers were recorded In 1931 height growth was extended from i5 em on June 1 to 35 cm by Tune 30 while in 1930 lesser showers and somewhat cooler temperatures permitted total height growth to reach only 23 em 01 about 35 pershycent less than in 1931

A contilluecl rise in tempeliLtures and a lack of precipitation in Inte June of both yems l1111ted 1urthel spring growth and started (llIing of the fomge

8 0 20 TEM~ERATU~E~ 1930~ ~~

60 15

V-I---

~ - ~t ~i- 10 is - PRECIPITATlON-s--

0 05~

I i II I I I I ~

I o bull o 1931 ~

~ 0 201l TEMPERATURgt-~ It

0 15[7 shy

-40 I 0

or h~PRECIPITAT~~ 2 05

I 1 -1 o I I I I I I I I o

0 - 1931 fROWT~

I l I ~ 1930 GROWT

0 ~

-A 1930 REGOOWTH 0

~ 0

MAR APR MAY JUNE JULY AUG SEPT OCT NOV FHlUllE ii-Ihe cUlIlulative growth 01 hluebunch whClltgrllSS (Agropyroll spicatum) lIud IU-duy HlllJIlllUifons

01 (OUlpcru(lIrc nnd precipitution 1930 nnd 1931

Significnntly diflerent lilnge conditions prevnilecl during the fnJl of these 2 years-again lfugely due toclifIerences ill plecipitntioll In 1930 precipitation wus very beavy in 1931 storms were light Ilnd scattered As u result there was nmiddot considerable amouut of regrowth in August and September of 1930 but practically none in 1931 Tlus legrowth in 1930 more than offset the short spring growth and in genoml created excelleD t early faU grazing couditions The advantage C1ented by ] 930 fllu weather did 110t bold bowover In November a Sllowstorm so deeply covered the runge tlmt the sheep hnd to be moved to feod lots L month earlier thun usual On the other hand henvy SllOWS did not come nutillato December 1931 so tha t it was possible ill tlHLt ear to 11 tilize pmctically aU of the fivniJshy

14 TECHNICAL BULLETIN (j 0 0 U DEPT OF GRTCUJJTum

able feed on the ground before moving to the winter rnnge and feed lots

The records of these 2 years show very clearly the combined action of climatic forces in determining the grazing periods from year to year whereby the start and early development of range forage is largely controlled by temperature precipitation becomes a major influence during late spring summer and fall Lnd temperature and precipitation combined det0rmil1e whether the dose of the fnU grazing period shaU be early or Ia teo

From a prndical l11tLnagemen t standpoint the Jolutively short range in the elates on which grnsses rench 2-inch height growth (18 days) dearly suggests that the average date for this stage of growth (Apr 22 1923-32) should bo used as the date for starting spring grazing and as a bnsis for planning the yeur-long cnlenelar of opemtion There are several advantages in the use of this base Sinee this date is likely to be nt aU times within about 8 duys of accuracy 8 to ] 0 days of supplem0n tal feed is needed in reserve as insura[lce agninst a shortage of mnge fornge in occnsional years of delayed growth as compared to the 18- to 20-clay feed supply that would be needed if start of growth 01e the hnsis Further 2-ineb height growth of grasses provides forage sufficient to insure the maintenance of ewes in good condition and normal gnins in lamb weight and denlopment Lastly when the fomge is gmzed by the proper llumbers a lflrge part of it will reach advaneed stages or development befort heing cropped permitting the production of seed and the res tora1iion of vigor hy plants on at least a pnrt of the runge ench year

Tbo close of tho fall glflzing sen SOil would naturall)r he planned for the flvcmge dnte on whieh deep snow may he eXp(ctNI But snow occurrence is so vurinbJe that at lcnst it 30-d1lY ]esorvo supply of hay and su])plements 01 tlwil equivttirnti in winter runge should he maintained in nddition to 1l1O nonnnl requJJcments for the winter period

The utilizutioll or the experiment-stntioll mnge in the spring and full is planned in accordnnee with the nYILilnhility of the fomgo and the exigencies of climnte imwfnr ns this is prHeticul Bcginning in 1930 the shc(p (1( tUlllrd out 011 the range ett(h yenr when the gltlsses IlflcL rondlCd 2-ineh growth Sh(~ep W(IO l(Il1ovod hom the range nbou t Decemher 1 although in some yeurs it hit o((u possible to use tho 11l nfe up 10 JanunImiddotY 1 and in others fltlCh ns 1910 tLnd 1932 snow closed the grn7ing senson about the middle of -iIovmllhcr

INFIUENCE O~ CLll1Al~ ON ~OItAta IIWDUCIION

The most obvious influ(llc( of elimateltnJOIt (Bp(eiully pIceipitllshytion-on the spril1g-JnlllHnge is in the YOlUlll( of Jornge produced 110111

yenr to year nnci therefore in the llumbers of stock that Cflll be glUzed on a giYen unit over u period of y(~nJmiddots Tho influence of climate 011

forage production JIIlS been obselTed OllllHlfes in the Southwest (4 6) and in Utah (2 7) but not on the sngeblush-whentgruss runge typc of southerll Idnho In the pres(11t study the illfluence of precipitntion on forage production on spring-full mnge is indicnted by the mUIlIler

in which the flveruge volume of J(gt(ld on two of the SO-ncro experimentnl paddocks fluctunted fronl y(111 to yel1r during the ppJiod 1924-32 One of the pnddoeks lIsed in this plll1se of the qtudy (paddock 1) was

INFLUJmCB OF GRAZING ON SPRIN(-FALL SHEEP RANGI~ 15

grazed only late in the faU the other (paddock 7) was grazed modshyerately for an approximate average period of 3 weeks in the spring t1fter grasses reached i-inch height growth and again in the fnl1 Because the major use of these mens wns obtained in the fall nfter plant growth wns completed it is considered that grazing hns been a relatively minor factor in fomge production as compared to the effect of climate

Total forngc production 011 the average amounted to 5651 sheepshydays of feed per SO-acre paddock annually but the volume from yenr to yeur vuried ilregulully nbove and below this average respondshying rather closely to fluctuations in the occmrence of precipitation during tIle current spring and preceding winter period (Oct 1 to June 30) as shown in Jigure 6 For exumple forage production wus 41 23 and 7 plrcent above UTerage in 1925 1932 and 1929 lespe~shytinly During thlse years precipitation wus also nboye the studyshy

s-wL shy

1 LA~

I AVERAGEP-- -7- --- -- shy I

L -t- 1~1--7 71HEI II I

I

I I AVERAGE

565ISHWllYS

~V lt ~ FORAGE PRODUCTION~ I

I

1924 1925 1926 1927 1926 1929 1930 1931 1932

1~Wlmiddotltlmiddot G-Fural-t(~ Pf(JdUl1tioli nnd willttlr-spriug pretinHution on two uxperimenta1 paddocks J92-1-a2

period UY(Iage ill til( will tlr untl spring seilsons Til] 928 1926 H124 nne 1nao fomge produetion WtlS 63 2010 ullci 8 p(Icent respectively below n (ruge find in eneh 01 these yenls precipitation wns also ddinitely su bnorll1nl In 2 of the yenn~ 1927 nnd 1931 both fomge ploduetioll and plt(~ipitution wer( nbout t1V(rnge A statistiCuJ I1nnlysis 01 tbe relntiollship b(tweell forage produetiull nlld precipitntiolt during the spring 1IlId prcc(ding winter yiplded 11

correlation cOlf1kient of OU44 which i eOllsidtrpd highly signifiennt 101 the lIumLwl of (liStS involld

The JI uetutltions in j()IugP prod u(tioll Oil thNw lueus were UIIshy

doubtedly due ill 1l1rgp lJI(1lSUI( to dif1tmiddotIlIW~S ill the growth of grHssPs not ollly b((n usn tlwfle plnnts (oJlstitut~~d t~ Illlljor portioll of the Iwailnbfe forllgt but 11180 bp(l1us( they nre espcdully sensitive to dlllnges in moisture Cllllditions This sllIsitidtY is seen in the mensulcd expansion alld lOutllletioll of the bnsnl trell of dumps of the glnss(s on foul 1IllLer-squnm [(lIced quadmts ns illustrated in figulc 7 lhe U PlIlge busalullIL of grllsses on thlse q uadrnts in 1923 wus G(sr (111 2 lhis ViiS ilHJ(HS(~d to 9MlR cm2 by 1926 through

16 TEChNICAL BULLETIN GOO U S DEP1 OF ACmWULTUHB

the expansion of individual clumps by tillering Although 1926 was a dry year the high density recorded on the quadmts in that year undoubtedly is a reflection of the exceptionally good growing condishytions of 1925 Conversely it appears that moisture in 1926 was inshysufficicnt to maintnin the expanded root systems nnd as a consequence the gmss clumps split into small plants lesulting in an averuge stand on the four plots of only 7365 cm2 in ] 927 The year of 1928 was again deficient in precipitntion and the nverage )asal area of the grasses decreased furchll to 4R4 cm2 in 1929 nnd to alow of 4762 cm2

in 1930 There was nn indication of respreading of the gruss clumps in 1931 and 1932 in which years the aVfrnge spread increased to 5]5 and 5425 cm~ In spite of this however uYrn~e bnsal area of the gmss(s in 1932 wns about J9 perccnt kss tlrnn In ] 923-not a SUIshy

1923 1924 1926 1926 1930 1932

Fwtlu i -Alllluni (hlllves ill hlSlll nrca of grnltS(s on four l1ngrllcd quudrats ilL lnitcd Stutes Shoop I~sperhlleut RltLtiOTl nlHl tht llvrrcslouding r~c()rd or willter4 spdng IlreclpitutioI1 lU2-1-32

prisiIlg J(lsult WJIPIl it is (oIlsidlrNl that prceipitntion during the period as a whole was ntJ(nsL 16 percent b(low llormnl for this 10u1lity

The yltrin bility in Joruge prod uetion reeordcd on this range is in genlJnl agreelllent with results obtuined by Nelson (6) ill studies of the bluek glHmn grnss ill the Southwest As in the Southwest the grlnt YilIinbility of forll~e produdioll from yenr to yenr enused by difl(middotPllces ill climate cfenTly indicates the futility of stocking the mllge on the bnsis of good 01 even avenlge yetuS as is commoll practice 011 w(stern rang ar(aes

INfLUENCE 0 CUMATE ON ItANGE SHEEP

Allimnl husbnndmtll Wll(lally hae recognized that the qunntity filld qunlity of Jeed uailable to livestock lIns a mnterial bearing 011

their thriftiu(ss aud produetidty The extcnt to which climate illshyfluPl)ees the productivity of runge sheep through its creet 011 forage growth lIns 1101 howey(l bePII so w(Jlund(Jstood especially on the spring-full mnge llnuy othe] fu(tOls l11e iIlYoh((l 011 this type of

INFLUENCE OF GRAZING ON SPRING-FALL SHBEP HANGE 17

range than the closely related elements of climate and plant growth These factors include effects as difficult to measure as cumulative improvement by breeding changes in methods of handling quality and quantity of winter feed and forage production on the summer range Moreover sheep are on the spring-fall range for only 2 to 3 months in the spring and in the fall The highly variable conditions to which Etneep are subjected during the entire year are indicated in the qualitative summary given in table 6

TABLE 6-A qualitative summary of seasonal conditions aifect-ing liXpcri1llentshy~ltatio1 sheep largely as a result of czi1llaticfactors 1924-32

---- Fall i t IFeedmiddotlot Is s Year n or Feci lot eondi prill Ulillner

runge I rUllg-a I Lions I II nmgo I rungo 1

----------_----------------- shyJaV8

11123-34bullbullbull_ ) I 70 r F p1924-U P 107 n B E

1925-26__ bull bullbull __ _ E E 47 1lt VI P 192J-27____ __ va P is G ( G 1927-18___bullbullbullbullbullbull__bullbullbull _____ bullbullbull _ o o M GOG 1928-29 __ ___ ___ _ G a 56 a r aa 11129-30__ _ __ bullbullbull F F 64 FOG 11l3G-3L __ E P 141 va l P 11l31-32_ _ P P 100 va l~ E___________---_--__-L__--__---_bull ____

I VP-very poor P=poor F rair O=good VO=vory good E=excelient bull Including Quality or hay bull Summer range conditions were average in 1929 but lumb~ were not IIhll1 to rClOV(lf from the sftmiddothack

caused bya very unravorable spring season

Although these variables made it impossible to isolate flnd evaluate the specific influence of climate on all aspects of runge sheep proshyduction on the spring-fllllrange it hilS been possible to deterIlline this influence on two important Ilspects namely the full weights of sheep and the number of lambs born

BODY WEIGHTS 01 lIAlUUE EWES

The average weights of 3-yeur-old Rambouillct und Corriedale ewes for the period 1925-33 Ilre given in table 7 These weights were taken in June after shearin~i in October at cullingi in 11te November when rams were turned ill and in early January when the rams were removed November and January weights were not started until the year 1927-28 and no weights werc taken in Jitnuary 1932 because of heavy snows and II hard trail that would have r(sulted in weights not representative of thn actunl condition of the sheep

TABLE 7-Seasonal Weight~ of 8-year-oltl Rambouillct (mel (orriedalc sheep at the United Stutes Sheep EX1)Crimcnt StatioJL dmiddotlring the 1)cdocl 1925-33

ltllmbouiilots Corrleduies

Year Juno October Nltt~~nt January JUlle October N~~~m January

-----~--imiddot----------------Poltnus POll-nds Polt7ld Pounds POlnds POl11lds Pou7Ids POU11d

1920-26___________ lOt 38 12200 l871 12220 _ __ 1926-27_____ 1Il3Sa 127711 bull 17 I) llO( bull __ bullbullbull _ 1927-28 ___ __ bullbullbull 1()1l3 115114 middotj2892 1177middot1 US 80 12754 middotirio -) i3~48 1928-29_ ____ 11535 12(17 11597 Jl207 11175 12-155 11588 11214 1l12li-30_ ___ bullbull __ 10773 130 IS 121 83 2100 10481 lao 42 13210 12471 11130-31 _____ _ 12387 11124 125011 1laquo111 U711 lm82 12S95 l~gtOl3 11l3-32__ _ _ lmIlB 1IIoB 12(188 _ 12400 13209 12787 11l32-33__ ____ 121 (jr 1J86-1 )1491 la5 OS 121 Oil iaO411 13)70 11182

Weighted Ryeragc ___ li122 iO2l ~ l2i4t 10778 IS ltl ~~

14 TECHNICAL BULLETIN (j 0 0 U DEPT OF GRTCUJJTum

able feed on the ground before moving to the winter rnnge and feed lots

The records of these 2 years show very clearly the combined action of climatic forces in determining the grazing periods from year to year whereby the start and early development of range forage is largely controlled by temperature precipitation becomes a major influence during late spring summer and fall Lnd temperature and precipitation combined det0rmil1e whether the dose of the fnU grazing period shaU be early or Ia teo

From a prndical l11tLnagemen t standpoint the Jolutively short range in the elates on which grnsses rench 2-inch height growth (18 days) dearly suggests that the average date for this stage of growth (Apr 22 1923-32) should bo used as the date for starting spring grazing and as a bnsis for planning the yeur-long cnlenelar of opemtion There are several advantages in the use of this base Sinee this date is likely to be nt aU times within about 8 duys of accuracy 8 to ] 0 days of supplem0n tal feed is needed in reserve as insura[lce agninst a shortage of mnge fornge in occnsional years of delayed growth as compared to the 18- to 20-clay feed supply that would be needed if start of growth 01e the hnsis Further 2-ineb height growth of grasses provides forage sufficient to insure the maintenance of ewes in good condition and normal gnins in lamb weight and denlopment Lastly when the fomge is gmzed by the proper llumbers a lflrge part of it will reach advaneed stages or development befort heing cropped permitting the production of seed and the res tora1iion of vigor hy plants on at least a pnrt of the runge ench year

Tbo close of tho fall glflzing sen SOil would naturall)r he planned for the flvcmge dnte on whieh deep snow may he eXp(ctNI But snow occurrence is so vurinbJe that at lcnst it 30-d1lY ]esorvo supply of hay and su])plements 01 tlwil equivttirnti in winter runge should he maintained in nddition to 1l1O nonnnl requJJcments for the winter period

The utilizutioll or the experiment-stntioll mnge in the spring and full is planned in accordnnee with the nYILilnhility of the fomgo and the exigencies of climnte imwfnr ns this is prHeticul Bcginning in 1930 the shc(p (1( tUlllrd out 011 the range ett(h yenr when the gltlsses IlflcL rondlCd 2-ineh growth Sh(~ep W(IO l(Il1ovod hom the range nbou t Decemher 1 although in some yeurs it hit o((u possible to use tho 11l nfe up 10 JanunImiddotY 1 and in others fltlCh ns 1910 tLnd 1932 snow closed the grn7ing senson about the middle of -iIovmllhcr

INFIUENCE O~ CLll1Al~ ON ~OItAta IIWDUCIION

The most obvious influ(llc( of elimateltnJOIt (Bp(eiully pIceipitllshytion-on the spril1g-JnlllHnge is in the YOlUlll( of Jornge produced 110111

yenr to year nnci therefore in the llumbers of stock that Cflll be glUzed on a giYen unit over u period of y(~nJmiddots Tho influence of climate 011

forage production JIIlS been obselTed OllllHlfes in the Southwest (4 6) and in Utah (2 7) but not on the sngeblush-whentgruss runge typc of southerll Idnho In the pres(11t study the illfluence of precipitntion on forage production on spring-full mnge is indicnted by the mUIlIler

in which the flveruge volume of J(gt(ld on two of the SO-ncro experimentnl paddocks fluctunted fronl y(111 to yel1r during the ppJiod 1924-32 One of the pnddoeks lIsed in this plll1se of the qtudy (paddock 1) was

INFLUJmCB OF GRAZING ON SPRIN(-FALL SHEEP RANGI~ 15

grazed only late in the faU the other (paddock 7) was grazed modshyerately for an approximate average period of 3 weeks in the spring t1fter grasses reached i-inch height growth and again in the fnl1 Because the major use of these mens wns obtained in the fall nfter plant growth wns completed it is considered that grazing hns been a relatively minor factor in fomge production as compared to the effect of climate

Total forngc production 011 the average amounted to 5651 sheepshydays of feed per SO-acre paddock annually but the volume from yenr to yeur vuried ilregulully nbove and below this average respondshying rather closely to fluctuations in the occmrence of precipitation during tIle current spring and preceding winter period (Oct 1 to June 30) as shown in Jigure 6 For exumple forage production wus 41 23 and 7 plrcent above UTerage in 1925 1932 and 1929 lespe~shytinly During thlse years precipitation wus also nboye the studyshy

s-wL shy

1 LA~

I AVERAGEP-- -7- --- -- shy I

L -t- 1~1--7 71HEI II I

I

I I AVERAGE

565ISHWllYS

~V lt ~ FORAGE PRODUCTION~ I

I

1924 1925 1926 1927 1926 1929 1930 1931 1932

1~Wlmiddotltlmiddot G-Fural-t(~ Pf(JdUl1tioli nnd willttlr-spriug pretinHution on two uxperimenta1 paddocks J92-1-a2

period UY(Iage ill til( will tlr untl spring seilsons Til] 928 1926 H124 nne 1nao fomge produetion WtlS 63 2010 ullci 8 p(Icent respectively below n (ruge find in eneh 01 these yenls precipitation wns also ddinitely su bnorll1nl In 2 of the yenn~ 1927 nnd 1931 both fomge ploduetioll and plt(~ipitution wer( nbout t1V(rnge A statistiCuJ I1nnlysis 01 tbe relntiollship b(tweell forage produetiull nlld precipitntiolt during the spring 1IlId prcc(ding winter yiplded 11

correlation cOlf1kient of OU44 which i eOllsidtrpd highly signifiennt 101 the lIumLwl of (liStS involld

The JI uetutltions in j()IugP prod u(tioll Oil thNw lueus were UIIshy

doubtedly due ill 1l1rgp lJI(1lSUI( to dif1tmiddotIlIW~S ill the growth of grHssPs not ollly b((n usn tlwfle plnnts (oJlstitut~~d t~ Illlljor portioll of the Iwailnbfe forllgt but 11180 bp(l1us( they nre espcdully sensitive to dlllnges in moisture Cllllditions This sllIsitidtY is seen in the mensulcd expansion alld lOutllletioll of the bnsnl trell of dumps of the glnss(s on foul 1IllLer-squnm [(lIced quadmts ns illustrated in figulc 7 lhe U PlIlge busalullIL of grllsses on thlse q uadrnts in 1923 wus G(sr (111 2 lhis ViiS ilHJ(HS(~d to 9MlR cm2 by 1926 through

16 TEChNICAL BULLETIN GOO U S DEP1 OF ACmWULTUHB

the expansion of individual clumps by tillering Although 1926 was a dry year the high density recorded on the quadmts in that year undoubtedly is a reflection of the exceptionally good growing condishytions of 1925 Conversely it appears that moisture in 1926 was inshysufficicnt to maintnin the expanded root systems nnd as a consequence the gmss clumps split into small plants lesulting in an averuge stand on the four plots of only 7365 cm2 in ] 927 The year of 1928 was again deficient in precipitntion and the nverage )asal area of the grasses decreased furchll to 4R4 cm2 in 1929 nnd to alow of 4762 cm2

in 1930 There was nn indication of respreading of the gruss clumps in 1931 and 1932 in which years the aVfrnge spread increased to 5]5 and 5425 cm~ In spite of this however uYrn~e bnsal area of the gmss(s in 1932 wns about J9 perccnt kss tlrnn In ] 923-not a SUIshy

1923 1924 1926 1926 1930 1932

Fwtlu i -Alllluni (hlllves ill hlSlll nrca of grnltS(s on four l1ngrllcd quudrats ilL lnitcd Stutes Shoop I~sperhlleut RltLtiOTl nlHl tht llvrrcslouding r~c()rd or willter4 spdng IlreclpitutioI1 lU2-1-32

prisiIlg J(lsult WJIPIl it is (oIlsidlrNl that prceipitntion during the period as a whole was ntJ(nsL 16 percent b(low llormnl for this 10u1lity

The yltrin bility in Joruge prod uetion reeordcd on this range is in genlJnl agreelllent with results obtuined by Nelson (6) ill studies of the bluek glHmn grnss ill the Southwest As in the Southwest the grlnt YilIinbility of forll~e produdioll from yenr to yenr enused by difl(middotPllces ill climate cfenTly indicates the futility of stocking the mllge on the bnsis of good 01 even avenlge yetuS as is commoll practice 011 w(stern rang ar(aes

INfLUENCE 0 CUMATE ON ItANGE SHEEP

Allimnl husbnndmtll Wll(lally hae recognized that the qunntity filld qunlity of Jeed uailable to livestock lIns a mnterial bearing 011

their thriftiu(ss aud produetidty The extcnt to which climate illshyfluPl)ees the productivity of runge sheep through its creet 011 forage growth lIns 1101 howey(l bePII so w(Jlund(Jstood especially on the spring-full mnge llnuy othe] fu(tOls l11e iIlYoh((l 011 this type of

INFLUENCE OF GRAZING ON SPRING-FALL SHBEP HANGE 17

range than the closely related elements of climate and plant growth These factors include effects as difficult to measure as cumulative improvement by breeding changes in methods of handling quality and quantity of winter feed and forage production on the summer range Moreover sheep are on the spring-fall range for only 2 to 3 months in the spring and in the fall The highly variable conditions to which Etneep are subjected during the entire year are indicated in the qualitative summary given in table 6

TABLE 6-A qualitative summary of seasonal conditions aifect-ing liXpcri1llentshy~ltatio1 sheep largely as a result of czi1llaticfactors 1924-32

---- Fall i t IFeedmiddotlot Is s Year n or Feci lot eondi prill Ulillner

runge I rUllg-a I Lions I II nmgo I rungo 1

----------_----------------- shyJaV8

11123-34bullbullbull_ ) I 70 r F p1924-U P 107 n B E

1925-26__ bull bullbull __ _ E E 47 1lt VI P 192J-27____ __ va P is G ( G 1927-18___bullbullbullbullbullbull__bullbullbull _____ bullbullbull _ o o M GOG 1928-29 __ ___ ___ _ G a 56 a r aa 11129-30__ _ __ bullbullbull F F 64 FOG 11l3G-3L __ E P 141 va l P 11l31-32_ _ P P 100 va l~ E___________---_--__-L__--__---_bull ____

I VP-very poor P=poor F rair O=good VO=vory good E=excelient bull Including Quality or hay bull Summer range conditions were average in 1929 but lumb~ were not IIhll1 to rClOV(lf from the sftmiddothack

caused bya very unravorable spring season

Although these variables made it impossible to isolate flnd evaluate the specific influence of climate on all aspects of runge sheep proshyduction on the spring-fllllrange it hilS been possible to deterIlline this influence on two important Ilspects namely the full weights of sheep and the number of lambs born

BODY WEIGHTS 01 lIAlUUE EWES

The average weights of 3-yeur-old Rambouillct und Corriedale ewes for the period 1925-33 Ilre given in table 7 These weights were taken in June after shearin~i in October at cullingi in 11te November when rams were turned ill and in early January when the rams were removed November and January weights were not started until the year 1927-28 and no weights werc taken in Jitnuary 1932 because of heavy snows and II hard trail that would have r(sulted in weights not representative of thn actunl condition of the sheep

TABLE 7-Seasonal Weight~ of 8-year-oltl Rambouillct (mel (orriedalc sheep at the United Stutes Sheep EX1)Crimcnt StatioJL dmiddotlring the 1)cdocl 1925-33

ltllmbouiilots Corrleduies

Year Juno October Nltt~~nt January JUlle October N~~~m January

-----~--imiddot----------------Poltnus POll-nds Polt7ld Pounds POlnds POl11lds Pou7Ids POU11d

1920-26___________ lOt 38 12200 l871 12220 _ __ 1926-27_____ 1Il3Sa 127711 bull 17 I) llO( bull __ bullbullbull _ 1927-28 ___ __ bullbullbull 1()1l3 115114 middotj2892 1177middot1 US 80 12754 middotirio -) i3~48 1928-29_ ____ 11535 12(17 11597 Jl207 11175 12-155 11588 11214 1l12li-30_ ___ bullbull __ 10773 130 IS 121 83 2100 10481 lao 42 13210 12471 11130-31 _____ _ 12387 11124 125011 1laquo111 U711 lm82 12S95 l~gtOl3 11l3-32__ _ _ lmIlB 1IIoB 12(188 _ 12400 13209 12787 11l32-33__ ____ 121 (jr 1J86-1 )1491 la5 OS 121 Oil iaO411 13)70 11182

Weighted Ryeragc ___ li122 iO2l ~ l2i4t 10778 IS ltl ~~

INFLUJmCB OF GRAZING ON SPRIN(-FALL SHEEP RANGI~ 15

grazed only late in the faU the other (paddock 7) was grazed modshyerately for an approximate average period of 3 weeks in the spring t1fter grasses reached i-inch height growth and again in the fnl1 Because the major use of these mens wns obtained in the fall nfter plant growth wns completed it is considered that grazing hns been a relatively minor factor in fomge production as compared to the effect of climate

Total forngc production 011 the average amounted to 5651 sheepshydays of feed per SO-acre paddock annually but the volume from yenr to yeur vuried ilregulully nbove and below this average respondshying rather closely to fluctuations in the occmrence of precipitation during tIle current spring and preceding winter period (Oct 1 to June 30) as shown in Jigure 6 For exumple forage production wus 41 23 and 7 plrcent above UTerage in 1925 1932 and 1929 lespe~shytinly During thlse years precipitation wus also nboye the studyshy

s-wL shy

1 LA~

I AVERAGEP-- -7- --- -- shy I

L -t- 1~1--7 71HEI II I

I

I I AVERAGE

565ISHWllYS

~V lt ~ FORAGE PRODUCTION~ I

I

1924 1925 1926 1927 1926 1929 1930 1931 1932

1~Wlmiddotltlmiddot G-Fural-t(~ Pf(JdUl1tioli nnd willttlr-spriug pretinHution on two uxperimenta1 paddocks J92-1-a2

period UY(Iage ill til( will tlr untl spring seilsons Til] 928 1926 H124 nne 1nao fomge produetion WtlS 63 2010 ullci 8 p(Icent respectively below n (ruge find in eneh 01 these yenls precipitation wns also ddinitely su bnorll1nl In 2 of the yenn~ 1927 nnd 1931 both fomge ploduetioll and plt(~ipitution wer( nbout t1V(rnge A statistiCuJ I1nnlysis 01 tbe relntiollship b(tweell forage produetiull nlld precipitntiolt during the spring 1IlId prcc(ding winter yiplded 11

correlation cOlf1kient of OU44 which i eOllsidtrpd highly signifiennt 101 the lIumLwl of (liStS involld

The JI uetutltions in j()IugP prod u(tioll Oil thNw lueus were UIIshy

doubtedly due ill 1l1rgp lJI(1lSUI( to dif1tmiddotIlIW~S ill the growth of grHssPs not ollly b((n usn tlwfle plnnts (oJlstitut~~d t~ Illlljor portioll of the Iwailnbfe forllgt but 11180 bp(l1us( they nre espcdully sensitive to dlllnges in moisture Cllllditions This sllIsitidtY is seen in the mensulcd expansion alld lOutllletioll of the bnsnl trell of dumps of the glnss(s on foul 1IllLer-squnm [(lIced quadmts ns illustrated in figulc 7 lhe U PlIlge busalullIL of grllsses on thlse q uadrnts in 1923 wus G(sr (111 2 lhis ViiS ilHJ(HS(~d to 9MlR cm2 by 1926 through

16 TEChNICAL BULLETIN GOO U S DEP1 OF ACmWULTUHB

the expansion of individual clumps by tillering Although 1926 was a dry year the high density recorded on the quadmts in that year undoubtedly is a reflection of the exceptionally good growing condishytions of 1925 Conversely it appears that moisture in 1926 was inshysufficicnt to maintnin the expanded root systems nnd as a consequence the gmss clumps split into small plants lesulting in an averuge stand on the four plots of only 7365 cm2 in ] 927 The year of 1928 was again deficient in precipitntion and the nverage )asal area of the grasses decreased furchll to 4R4 cm2 in 1929 nnd to alow of 4762 cm2

in 1930 There was nn indication of respreading of the gruss clumps in 1931 and 1932 in which years the aVfrnge spread increased to 5]5 and 5425 cm~ In spite of this however uYrn~e bnsal area of the gmss(s in 1932 wns about J9 perccnt kss tlrnn In ] 923-not a SUIshy

1923 1924 1926 1926 1930 1932

Fwtlu i -Alllluni (hlllves ill hlSlll nrca of grnltS(s on four l1ngrllcd quudrats ilL lnitcd Stutes Shoop I~sperhlleut RltLtiOTl nlHl tht llvrrcslouding r~c()rd or willter4 spdng IlreclpitutioI1 lU2-1-32

prisiIlg J(lsult WJIPIl it is (oIlsidlrNl that prceipitntion during the period as a whole was ntJ(nsL 16 percent b(low llormnl for this 10u1lity

The yltrin bility in Joruge prod uetion reeordcd on this range is in genlJnl agreelllent with results obtuined by Nelson (6) ill studies of the bluek glHmn grnss ill the Southwest As in the Southwest the grlnt YilIinbility of forll~e produdioll from yenr to yenr enused by difl(middotPllces ill climate cfenTly indicates the futility of stocking the mllge on the bnsis of good 01 even avenlge yetuS as is commoll practice 011 w(stern rang ar(aes

INfLUENCE 0 CUMATE ON ItANGE SHEEP

Allimnl husbnndmtll Wll(lally hae recognized that the qunntity filld qunlity of Jeed uailable to livestock lIns a mnterial bearing 011

their thriftiu(ss aud produetidty The extcnt to which climate illshyfluPl)ees the productivity of runge sheep through its creet 011 forage growth lIns 1101 howey(l bePII so w(Jlund(Jstood especially on the spring-full mnge llnuy othe] fu(tOls l11e iIlYoh((l 011 this type of

INFLUENCE OF GRAZING ON SPRING-FALL SHBEP HANGE 17

range than the closely related elements of climate and plant growth These factors include effects as difficult to measure as cumulative improvement by breeding changes in methods of handling quality and quantity of winter feed and forage production on the summer range Moreover sheep are on the spring-fall range for only 2 to 3 months in the spring and in the fall The highly variable conditions to which Etneep are subjected during the entire year are indicated in the qualitative summary given in table 6

TABLE 6-A qualitative summary of seasonal conditions aifect-ing liXpcri1llentshy~ltatio1 sheep largely as a result of czi1llaticfactors 1924-32

---- Fall i t IFeedmiddotlot Is s Year n or Feci lot eondi prill Ulillner

runge I rUllg-a I Lions I II nmgo I rungo 1

----------_----------------- shyJaV8

11123-34bullbullbull_ ) I 70 r F p1924-U P 107 n B E

1925-26__ bull bullbull __ _ E E 47 1lt VI P 192J-27____ __ va P is G ( G 1927-18___bullbullbullbullbullbull__bullbullbull _____ bullbullbull _ o o M GOG 1928-29 __ ___ ___ _ G a 56 a r aa 11129-30__ _ __ bullbullbull F F 64 FOG 11l3G-3L __ E P 141 va l P 11l31-32_ _ P P 100 va l~ E___________---_--__-L__--__---_bull ____

I VP-very poor P=poor F rair O=good VO=vory good E=excelient bull Including Quality or hay bull Summer range conditions were average in 1929 but lumb~ were not IIhll1 to rClOV(lf from the sftmiddothack

caused bya very unravorable spring season

Although these variables made it impossible to isolate flnd evaluate the specific influence of climate on all aspects of runge sheep proshyduction on the spring-fllllrange it hilS been possible to deterIlline this influence on two important Ilspects namely the full weights of sheep and the number of lambs born

BODY WEIGHTS 01 lIAlUUE EWES

The average weights of 3-yeur-old Rambouillct und Corriedale ewes for the period 1925-33 Ilre given in table 7 These weights were taken in June after shearin~i in October at cullingi in 11te November when rams were turned ill and in early January when the rams were removed November and January weights were not started until the year 1927-28 and no weights werc taken in Jitnuary 1932 because of heavy snows and II hard trail that would have r(sulted in weights not representative of thn actunl condition of the sheep

TABLE 7-Seasonal Weight~ of 8-year-oltl Rambouillct (mel (orriedalc sheep at the United Stutes Sheep EX1)Crimcnt StatioJL dmiddotlring the 1)cdocl 1925-33

ltllmbouiilots Corrleduies

Year Juno October Nltt~~nt January JUlle October N~~~m January

-----~--imiddot----------------Poltnus POll-nds Polt7ld Pounds POlnds POl11lds Pou7Ids POU11d

1920-26___________ lOt 38 12200 l871 12220 _ __ 1926-27_____ 1Il3Sa 127711 bull 17 I) llO( bull __ bullbullbull _ 1927-28 ___ __ bullbullbull 1()1l3 115114 middotj2892 1177middot1 US 80 12754 middotirio -) i3~48 1928-29_ ____ 11535 12(17 11597 Jl207 11175 12-155 11588 11214 1l12li-30_ ___ bullbull __ 10773 130 IS 121 83 2100 10481 lao 42 13210 12471 11130-31 _____ _ 12387 11124 125011 1laquo111 U711 lm82 12S95 l~gtOl3 11l3-32__ _ _ lmIlB 1IIoB 12(188 _ 12400 13209 12787 11l32-33__ ____ 121 (jr 1J86-1 )1491 la5 OS 121 Oil iaO411 13)70 11182

Weighted Ryeragc ___ li122 iO2l ~ l2i4t 10778 IS ltl ~~

16 TEChNICAL BULLETIN GOO U S DEP1 OF ACmWULTUHB

the expansion of individual clumps by tillering Although 1926 was a dry year the high density recorded on the quadmts in that year undoubtedly is a reflection of the exceptionally good growing condishytions of 1925 Conversely it appears that moisture in 1926 was inshysufficicnt to maintnin the expanded root systems nnd as a consequence the gmss clumps split into small plants lesulting in an averuge stand on the four plots of only 7365 cm2 in ] 927 The year of 1928 was again deficient in precipitntion and the nverage )asal area of the grasses decreased furchll to 4R4 cm2 in 1929 nnd to alow of 4762 cm2

in 1930 There was nn indication of respreading of the gruss clumps in 1931 and 1932 in which years the aVfrnge spread increased to 5]5 and 5425 cm~ In spite of this however uYrn~e bnsal area of the gmss(s in 1932 wns about J9 perccnt kss tlrnn In ] 923-not a SUIshy

1923 1924 1926 1926 1930 1932

Fwtlu i -Alllluni (hlllves ill hlSlll nrca of grnltS(s on four l1ngrllcd quudrats ilL lnitcd Stutes Shoop I~sperhlleut RltLtiOTl nlHl tht llvrrcslouding r~c()rd or willter4 spdng IlreclpitutioI1 lU2-1-32

prisiIlg J(lsult WJIPIl it is (oIlsidlrNl that prceipitntion during the period as a whole was ntJ(nsL 16 percent b(low llormnl for this 10u1lity

The yltrin bility in Joruge prod uetion reeordcd on this range is in genlJnl agreelllent with results obtuined by Nelson (6) ill studies of the bluek glHmn grnss ill the Southwest As in the Southwest the grlnt YilIinbility of forll~e produdioll from yenr to yenr enused by difl(middotPllces ill climate cfenTly indicates the futility of stocking the mllge on the bnsis of good 01 even avenlge yetuS as is commoll practice 011 w(stern rang ar(aes

INfLUENCE 0 CUMATE ON ItANGE SHEEP

Allimnl husbnndmtll Wll(lally hae recognized that the qunntity filld qunlity of Jeed uailable to livestock lIns a mnterial bearing 011

their thriftiu(ss aud produetidty The extcnt to which climate illshyfluPl)ees the productivity of runge sheep through its creet 011 forage growth lIns 1101 howey(l bePII so w(Jlund(Jstood especially on the spring-full mnge llnuy othe] fu(tOls l11e iIlYoh((l 011 this type of

INFLUENCE OF GRAZING ON SPRING-FALL SHBEP HANGE 17

range than the closely related elements of climate and plant growth These factors include effects as difficult to measure as cumulative improvement by breeding changes in methods of handling quality and quantity of winter feed and forage production on the summer range Moreover sheep are on the spring-fall range for only 2 to 3 months in the spring and in the fall The highly variable conditions to which Etneep are subjected during the entire year are indicated in the qualitative summary given in table 6

TABLE 6-A qualitative summary of seasonal conditions aifect-ing liXpcri1llentshy~ltatio1 sheep largely as a result of czi1llaticfactors 1924-32

---- Fall i t IFeedmiddotlot Is s Year n or Feci lot eondi prill Ulillner

runge I rUllg-a I Lions I II nmgo I rungo 1

----------_----------------- shyJaV8

11123-34bullbullbull_ ) I 70 r F p1924-U P 107 n B E

1925-26__ bull bullbull __ _ E E 47 1lt VI P 192J-27____ __ va P is G ( G 1927-18___bullbullbullbullbullbull__bullbullbull _____ bullbullbull _ o o M GOG 1928-29 __ ___ ___ _ G a 56 a r aa 11129-30__ _ __ bullbullbull F F 64 FOG 11l3G-3L __ E P 141 va l P 11l31-32_ _ P P 100 va l~ E___________---_--__-L__--__---_bull ____

I VP-very poor P=poor F rair O=good VO=vory good E=excelient bull Including Quality or hay bull Summer range conditions were average in 1929 but lumb~ were not IIhll1 to rClOV(lf from the sftmiddothack

caused bya very unravorable spring season

Although these variables made it impossible to isolate flnd evaluate the specific influence of climate on all aspects of runge sheep proshyduction on the spring-fllllrange it hilS been possible to deterIlline this influence on two important Ilspects namely the full weights of sheep and the number of lambs born

BODY WEIGHTS 01 lIAlUUE EWES

The average weights of 3-yeur-old Rambouillct und Corriedale ewes for the period 1925-33 Ilre given in table 7 These weights were taken in June after shearin~i in October at cullingi in 11te November when rams were turned ill and in early January when the rams were removed November and January weights were not started until the year 1927-28 and no weights werc taken in Jitnuary 1932 because of heavy snows and II hard trail that would have r(sulted in weights not representative of thn actunl condition of the sheep

TABLE 7-Seasonal Weight~ of 8-year-oltl Rambouillct (mel (orriedalc sheep at the United Stutes Sheep EX1)Crimcnt StatioJL dmiddotlring the 1)cdocl 1925-33

ltllmbouiilots Corrleduies

Year Juno October Nltt~~nt January JUlle October N~~~m January

-----~--imiddot----------------Poltnus POll-nds Polt7ld Pounds POlnds POl11lds Pou7Ids POU11d

1920-26___________ lOt 38 12200 l871 12220 _ __ 1926-27_____ 1Il3Sa 127711 bull 17 I) llO( bull __ bullbullbull _ 1927-28 ___ __ bullbullbull 1()1l3 115114 middotj2892 1177middot1 US 80 12754 middotirio -) i3~48 1928-29_ ____ 11535 12(17 11597 Jl207 11175 12-155 11588 11214 1l12li-30_ ___ bullbull __ 10773 130 IS 121 83 2100 10481 lao 42 13210 12471 11130-31 _____ _ 12387 11124 125011 1laquo111 U711 lm82 12S95 l~gtOl3 11l3-32__ _ _ lmIlB 1IIoB 12(188 _ 12400 13209 12787 11l32-33__ ____ 121 (jr 1J86-1 )1491 la5 OS 121 Oil iaO411 13)70 11182

Weighted Ryeragc ___ li122 iO2l ~ l2i4t 10778 IS ltl ~~

INFLUENCE OF GRAZING ON SPRING-FALL SHBEP HANGE 17

range than the closely related elements of climate and plant growth These factors include effects as difficult to measure as cumulative improvement by breeding changes in methods of handling quality and quantity of winter feed and forage production on the summer range Moreover sheep are on the spring-fall range for only 2 to 3 months in the spring and in the fall The highly variable conditions to which Etneep are subjected during the entire year are indicated in the qualitative summary given in table 6

TABLE 6-A qualitative summary of seasonal conditions aifect-ing liXpcri1llentshy~ltatio1 sheep largely as a result of czi1llaticfactors 1924-32

---- Fall i t IFeedmiddotlot Is s Year n or Feci lot eondi prill Ulillner

runge I rUllg-a I Lions I II nmgo I rungo 1

----------_----------------- shyJaV8

11123-34bullbullbull_ ) I 70 r F p1924-U P 107 n B E

1925-26__ bull bullbull __ _ E E 47 1lt VI P 192J-27____ __ va P is G ( G 1927-18___bullbullbullbullbullbull__bullbullbull _____ bullbullbull _ o o M GOG 1928-29 __ ___ ___ _ G a 56 a r aa 11129-30__ _ __ bullbullbull F F 64 FOG 11l3G-3L __ E P 141 va l P 11l31-32_ _ P P 100 va l~ E___________---_--__-L__--__---_bull ____

I VP-very poor P=poor F rair O=good VO=vory good E=excelient bull Including Quality or hay bull Summer range conditions were average in 1929 but lumb~ were not IIhll1 to rClOV(lf from the sftmiddothack

caused bya very unravorable spring season

Although these variables made it impossible to isolate flnd evaluate the specific influence of climate on all aspects of runge sheep proshyduction on the spring-fllllrange it hilS been possible to deterIlline this influence on two important Ilspects namely the full weights of sheep and the number of lambs born

BODY WEIGHTS 01 lIAlUUE EWES

The average weights of 3-yeur-old Rambouillct und Corriedale ewes for the period 1925-33 Ilre given in table 7 These weights were taken in June after shearin~i in October at cullingi in 11te November when rams were turned ill and in early January when the rams were removed November and January weights were not started until the year 1927-28 and no weights werc taken in Jitnuary 1932 because of heavy snows and II hard trail that would have r(sulted in weights not representative of thn actunl condition of the sheep

TABLE 7-Seasonal Weight~ of 8-year-oltl Rambouillct (mel (orriedalc sheep at the United Stutes Sheep EX1)Crimcnt StatioJL dmiddotlring the 1)cdocl 1925-33

ltllmbouiilots Corrleduies

Year Juno October Nltt~~nt January JUlle October N~~~m January

-----~--imiddot----------------Poltnus POll-nds Polt7ld Pounds POlnds POl11lds Pou7Ids POU11d

1920-26___________ lOt 38 12200 l871 12220 _ __ 1926-27_____ 1Il3Sa 127711 bull 17 I) llO( bull __ bullbullbull _ 1927-28 ___ __ bullbullbull 1()1l3 115114 middotj2892 1177middot1 US 80 12754 middotirio -) i3~48 1928-29_ ____ 11535 12(17 11597 Jl207 11175 12-155 11588 11214 1l12li-30_ ___ bullbull __ 10773 130 IS 121 83 2100 10481 lao 42 13210 12471 11130-31 _____ _ 12387 11124 125011 1laquo111 U711 lm82 12S95 l~gtOl3 11l3-32__ _ _ lmIlB 1IIoB 12(188 _ 12400 13209 12787 11l32-33__ ____ 121 (jr 1J86-1 )1491 la5 OS 121 Oil iaO411 13)70 11182

Weighted Ryeragc ___ li122 iO2l ~ l2i4t 10778 IS ltl ~~

18 TJ~OHNICAL BULLETIN 600 U ~ DEPT OF AGRIOULTUHE

As might be expected both Rambouillet and Corriedale sheep weigh least in June after shearing and at a time when ewes are llUlsing lambs Weights are highest in October after the lambs are ~eai1ed and after the ewes have spent the summer on good moulltam range feed A gradual decrease in weight occurs in N ovellber and J~~uary prinCipally because of a chnnge to dry forage and mcreased difhculty of reaching the feed through deepening snow In the last years of the study there was a decided trend townrd increased weights and fluctuations in weights from year to year aboye and below the average for the period

~ ~

PRECIPITATION~~ jl

~~ ~bl hll ~

a ~

~ RAMBOUILLETSQl

~30r-----------------------------------------------~ 15 ~ tUf-shy

~

~I ~ ) ) CORRIEDALES ~301~--------------------------------------________~ liJ t ZOt- shy

~ ~ ~

1927 1929 1931 1932 fGUKE S-Gnins in wei~ht In Rllmbou1lctnlld Corrieonle ewes between Juntl nnd November 301927-32

with averuge sensonal (Apr 1 to Sept ao) prccipitltion for the sumo period

November weights are considered a reliable index of forage condishytions on spring-falllange Vihile it is true that they reflect the infiushyence of slimmer gmziug smnmer range conditions approximate so closely those of spring rtlllge (table 6) that for the pUlpose of establishshying the relationship between sheep condition and variations in wenther as 118re shown the srnnmer range period need not be segregated

The relation between annual fluctuations in weights of mature sheep and gencral range conditions arc iIlustmted in figure 8 wherein departures from avcrnge gains ill weight between efLI~JT June and late Novcmber during the VCHlmiddotS 1927 to 1932 Ille compared with average SCltsollai precipitation ~ TIw differcnce betwOltn June and November weights are used hecl1use tl1is most accull)tcly lellccts the stun of fornge quality and qut1utity during the spring summer uud fall grazshy

INJLUr~NCE OJ GUAZING ON SPHING-JALL SHEEP UANGB 19

ing periods Seasonal precipitation Amil 1 to September 30 likeshywise is an approximution of the general moisture conditions which prevailed on the spring-fall range und had a direct bearing on forage production

The heaviest gains of R1mbouillet and Uorriedale ewes reflect the favorable moisture conditions in 1927 1929 and 1932 Similarly the inadequate moisture for good fomge productioll in 1928 ulld 1931 is reflected in yery slight gnins for those yeurs with nil actual loss in the Rambouillet breed in 1931 The comparatively low gains in 1930 despite abundant moisture and flworable range conditions up to November are explained by the heavy snow ill November of that year which necessitnted a premature und hard tmil to the feed lots Weights obtained thereafter evidently leflect the effeets of tmiling rather than moisture conditions A somewhat similar eondition developed in 1932 but only the Corriedules were affected Lnd only slightly

These data show thnt over and aboye any improvcmeut in aduptshyability for making nnd muintuiuing good weights that is attained through breeding annual variations in weight may be expected to lesult from fluctuations in weather and forugo production Because of the relationship between sheep weights and forage the best insurance against severe losses in body weight during drought years is to stock the range 011 a sufficiently conservative basis so that eyen in the poorest years ample forage will be available for the sheep

LAMB lUODUCTION

The pounds of lamb produced pel ewe is one of the most important aspects of range sheep production and the mllnber of lambs boIll and born alive pel ewe bred is obiously of primury consideration The extent to which tho munbers of lumbs borll und boIll alio pel ewe flro rdfected by range conditions is indicated in n summary of this phase of lamb production for the period 1925-32 (table 8)

TABLE S-Summary of R(tmuollillct and COlrictialc lalllb 1Jrodllction at the United Slates Sheep Expciment Station 1925-32

HAM n011JLETS

1 Cltt I Ewes wilh lamb ILambs dropped by Lllmhs droppedYcmr I hreedlll i ewes bred alive b) ewes bred

----------- ----1---------1 ~Yllmber l~umlJfr l~erccnt lTu11lber Perrellt lYu71lber PerCfnl

1925 ___ __ _ __ ~~_ ~ 1l7 25 SO 44 21H 8a28 2111 81 0 1926bullbullbullbullbullbullbullbullbullbullbull la5 2ii 82 09 112 93 J3 ~JO 811 57 1027 lW 285 81 4l mo 8571 2middot1 70 [17 1928 125 27U 85 85 297 Ill as 277 85 21 1~29 (iIiO 48J 288 51(1 7Ro 18 430 6606 IOaO 42 ml HIa middotla7 lO234 410 9002 101 __ bull 217 2m) 854 320 IOU 71l ~~15 mla 1932 290 20R IKI fi4 215 Ill (i(i 275 112 II I

Totnl bull ~4iiO~~-----mi5~1~

(OHIUEDALES

20 TECHNICAL BULLETIN 600 U S DEPT OF AGRIOULTURE

For Rambouillets the average of 1699 percent of ewes not with lamb included all drys and all ewes dead or missing from breeding to lambing Percent of ewes with lamb varied by 1869 from 1929 to 1930 The number of Rambouillet lambs dropped per 100 ewes bred varied by 3158 and those dropped alive by 3327 between 1929 and 1931

LIVE LAMBS DROPPED PER 100 EWES 8RED

DEPARTURE FROM 8-YEAR AVERAGE

~

Ishy---

CJ l-

I I L---I AVERAGE 8901

--shy

-shy

16 1925 1926 1927 1928 1929 1930 1931 1932

12

SEASONAL PRECIPITATION OF PRECEDING YEAR-

~ --~I- Ishy -r--shy

--- - - I- r- - -I Jo

1924 1925 1926 1927 1928 1929 1930 1931 joOURE g-The aerage numher 01 lambs horn alive per 1110 ewes bred (nlllnboulllets and Corriedalesl In

relation to the seasonal precipitatfon (Apr I to Sept 30) 01 the proeedln yellr 1925-32

The Corriedale group were in general more productive and the range of varifltions from year to year was much smaller Difference in percent of ewes with lamb was 888 of lambs dropped ]759 and of lambs dropped alive 1921 The high years for the firstmiddot two items were 1930 and 1931 and the high year for lambs dropped alive was 1926 The low yel1r for Iambs dropped alive by both breeds was 1929

When the number of lambs horn and the number born alive per 100 (wes bred are compared with April to September precipitatIOn

I

JNFLUEXCE OF GRAZING ON SPIUNG-FAJ~L SHEBP RANGB 21

records (fig 9) it is noted that the lamb crop fluctuated from year to to vear closely in accordance with variations in moisture conditions which prevailed during the preceding year that is the number of lambs born alive was below average in 1925 1927 ond 1929 whereas preripitation duringeoch of the preceding yeals-1924 1926 and 1928shywas also below normal On the other hand the number of live lambs born in 1926 1928 1930 and 1931 was above average and these volues corresponded to favorable moisture conditions during each previous fall Similarly lamb production was relatively lower in 1932 than in 1931 as precipitation was lower in 1931 than in 1930 Thus it appearsthat ewes in a thrifty condition in the full nsthe result of abundant forage tend to produce more live lambs in the folshylowing spring than do ewes in a year following a poor fall

No consistent relationship appears between climate and later stages of lomb development such as pounds of guin per lamb from birth to weaning the numbers weaned per 100 ewes bred or the weaned weight of lambs and pounds of lamb produced per ewe Climate and the quantity and quality of forage on the spring-fall range undoubtedly have some effect on these phases of lamb production but it is obscured by other factors such as denth due to predators disease and straying slow development due to inferior breeding mothering and methods of handling and conditions on the summer range where the lambs motured (1)

Otber important aspects of range-sheep production including yields of wool and death losses varied from year to year during the period of study partly in response to climate and forage production but the presence of other factors precluded isolation and evaluation of the specific influence of climatie factors

GRAZING INFLUENCES

The important bearing that climate has on the growth and developshyment of forage from year to year on spring-fall mnge must be undershystood and be given careful consideration in establishing periods of use and a basic rate of stocking but thnt alone is not enough The influence of good years and bad years is a serious matter but the stark necessity of anticipating such climatic variations is not conshyvincingly apparent until studies have been carried further and have revealed the effect of time and intensity of grazin~ upon the range in years of drought and years of plenty Such studIeS of grazing influshyences make it dear that overgmzing may result in range depletion of n far more lasting and serious character than any temporary declines in productivity normally induced by drought alone (pI 2) The degree to which the sagebrush-bunchgrass type of spring-fall range land can be damaged by overgrazing in a relatively short period of years is shown in the results presented iTt the following pages These results were obtained from the four 8lJ-acre paddocks designated 2 3 8 and 7 nlready described Each paddock was utilized to different degrees and for different periods in the spring followed in each case by the removal of nearly all of the reml1imng forage in the full At the same time paddock 1 gll1zed only in the fall was held I1S a check area to show the maximum improvement that mightbave been expected under vrevailing climatic conditions during the period of the study

22 TECHNICAL BULLETIN 600 U S DEPT OJ AGRlCULTUng

RANGE DEPLETION RESULTING ROM HEAVY CONTINUOUS SPRING AND LAfE FALL GRAZING

The degree to which sugebrush-bunchgmss spring-full lILuge in Idaho can be depleted by heavy continuous spring and late fl111 grazing is illustrated by results obtained during the period 1924-32 on padshydock 2 Here approximlltely 68 percent of all available foruge WIIS utilized in the spring starting when grasses reached 2-inch height growth and ending at the close of the spring gmzing sellson nnd 25 percent was consumed in the fnll leaving on the average only 7 percent of the fomge unutilized (table 9)

TAHI~E fJ-Ltduol lise under hCUlI1f cOllti7L1111~ ~JiTing all(i l(lc fall graziny of 71arldock 2 1924-82

----------fI-Jr-iII-t~g-rll-1i-n-g --~Ii ---~-u-lI-gr-II-7i-rlh-middot---I-)-O-Ilr-I~-t-ot-n-I-E-S-ll-

1_____-___-__ - -------- t _-----_1 matedI middotmiddotmiddotmiddot-i--( totlll

Yonr 1001 JM I teol jltormiddot tool Formiddot lorage

Period oIuso n~n Plriuri or U$(~ n~c ago producshyrtlllgu u5ltJd mnge used runge used t10n 1

1- - ~~~~ j~~~ -- S~~V -- 8g~~ 1Jcr Prrmiddot per Per- 1Ja Permiddot per

IQ2L iAJ1r2o-May~1 ~~~~t cr~b O(IrX13 ~f~~ ce~~ ~g~82 a9~ a~ti~8u 1I2r _j Apr H-lllllC 15 i 112 12 72 (jet Jr-XO 111 2465 28 86117 JOO 8697 HI26 bullbull Apr J7-1Ilny27 I 17RO 115 KI IO-X 2() ]18 1 I08 08 3U78 1IJ27 pr10-Jlllloll 2middot142 66 Oct20-K(Ii 12A8 14 l090 100 36110 1928 bull Apr 2-Iuoo 8 2middot1 02 7(1 Olt 26-De(middot I 60a 21lJ 55 100 31 5r 1920 jIIln-JUIlO J2 lK i1 I 74 Oet 31-Ko I middot1 85 IU ~gtj 8 13 2535 lao AprbullbullW-IUIIO l~ 8(I~ ~~ No 5-0 Hi 6 ~6 ~n 111 O~ 116O 1931 Aprbullbull9-Iunc 1_ 10bull11 f NQ 2-No It 40 ao 1527 9 1514 193L f May I-Aug 0 li92 fl5 Ko Hromiddot 0 l3fJ 10 21 ~I 05 32 i8 ----- -~-~------

Acrage bullbull iApr25-Juno15 256[1 ~SIOCt2q-~Hi_ ~~j_a5161 ial 3i81

t EstiIIIllled [olal rllrn~o productloD (~hllpmiddotdIlYs plr Il(middotn) uverago 102middot1-25 O~l3 11)11-322middot120 Loss III lora~o vnluo hetween 1024-25 und 1031-a2 r) percent

(Oomputed average Sec loolnoto 4 p G

The rcspeeth-e tlYcruges for 1924-25 und 1931-82 and the difference in percent between them shown nt the bottom of table D are highly significnnt Sinee 1924 wns a very poor growth year while 1()25 was very good the uvcruge numbcr of sheep-duys of feed per ncre proshyduced in these 2 years is considered to be a reliable index of the proshyductivity of the pasture at the start of the grazing tests Similurly 1931 and 1932 were rclatively poor and good yeals rcspectivelYi hence the avernge of these 2 years is considered a fair index of the productivity of the nreH ut the end of the test period

Under this system und intensity of grazing the number of sheepshyduys of feed fluctuated about in accordance with growing conditions on the runge during the first 2 years of the study After the excepshytionolly good growth yeur of 1925 however und in spite of fairly fa orable growing conditions in 1927 und ] 929 the productivity of the posture deelined consistently to the low level of less thun 16 sheepshydays of fecd per uere in 1931 (fig 10) As the result of better-thanshyoverage growing conditions in 1932 n little more than twice as much Iornge was proclueed in that yenr but the uvernge of feed produeed in these lnst 2 yenrs wns 65 PlTCll1t less than the nverage of the first 2 yoals of the study

Coinei(cntaJ with the dedinl in the sheep-days of feed produced sigllificant changes occurred ill tho vegetative covcr (pI 3) Acshy

INJLUr~NCE OJ GUAZING ON SPHING-JALL SHEEP UANGB 19

ing periods Seasonal precipitation Amil 1 to September 30 likeshywise is an approximution of the general moisture conditions which prevailed on the spring-fall range und had a direct bearing on forage production

The heaviest gains of R1mbouillet and Uorriedale ewes reflect the favorable moisture conditions in 1927 1929 and 1932 Similarly the inadequate moisture for good fomge productioll in 1928 ulld 1931 is reflected in yery slight gnins for those yeurs with nil actual loss in the Rambouillet breed in 1931 The comparatively low gains in 1930 despite abundant moisture and flworable range conditions up to November are explained by the heavy snow ill November of that year which necessitnted a premature und hard tmil to the feed lots Weights obtained thereafter evidently leflect the effeets of tmiling rather than moisture conditions A somewhat similar eondition developed in 1932 but only the Corriedules were affected Lnd only slightly

These data show thnt over and aboye any improvcmeut in aduptshyability for making nnd muintuiuing good weights that is attained through breeding annual variations in weight may be expected to lesult from fluctuations in weather and forugo production Because of the relationship between sheep weights and forage the best insurance against severe losses in body weight during drought years is to stock the range 011 a sufficiently conservative basis so that eyen in the poorest years ample forage will be available for the sheep

LAMB lUODUCTION

The pounds of lamb produced pel ewe is one of the most important aspects of range sheep production and the mllnber of lambs boIll and born alive pel ewe bred is obiously of primury consideration The extent to which tho munbers of lumbs borll und boIll alio pel ewe flro rdfected by range conditions is indicated in n summary of this phase of lamb production for the period 1925-32 (table 8)

TABLE S-Summary of R(tmuollillct and COlrictialc lalllb 1Jrodllction at the United Slates Sheep Expciment Station 1925-32

HAM n011JLETS

1 Cltt I Ewes wilh lamb ILambs dropped by Lllmhs droppedYcmr I hreedlll i ewes bred alive b) ewes bred

----------- ----1---------1 ~Yllmber l~umlJfr l~erccnt lTu11lber Perrellt lYu71lber PerCfnl

1925 ___ __ _ __ ~~_ ~ 1l7 25 SO 44 21H 8a28 2111 81 0 1926bullbullbullbullbullbullbullbullbullbullbull la5 2ii 82 09 112 93 J3 ~JO 811 57 1027 lW 285 81 4l mo 8571 2middot1 70 [17 1928 125 27U 85 85 297 Ill as 277 85 21 1~29 (iIiO 48J 288 51(1 7Ro 18 430 6606 IOaO 42 ml HIa middotla7 lO234 410 9002 101 __ bull 217 2m) 854 320 IOU 71l ~~15 mla 1932 290 20R IKI fi4 215 Ill (i(i 275 112 II I

Totnl bull ~4iiO~~-----mi5~1~

(OHIUEDALES

20 TECHNICAL BULLETIN 600 U S DEPT OF AGRIOULTURE

For Rambouillets the average of 1699 percent of ewes not with lamb included all drys and all ewes dead or missing from breeding to lambing Percent of ewes with lamb varied by 1869 from 1929 to 1930 The number of Rambouillet lambs dropped per 100 ewes bred varied by 3158 and those dropped alive by 3327 between 1929 and 1931

LIVE LAMBS DROPPED PER 100 EWES 8RED

DEPARTURE FROM 8-YEAR AVERAGE

~

Ishy---

CJ l-

I I L---I AVERAGE 8901

--shy

-shy

16 1925 1926 1927 1928 1929 1930 1931 1932

12

SEASONAL PRECIPITATION OF PRECEDING YEAR-

~ --~I- Ishy -r--shy

--- - - I- r- - -I Jo

1924 1925 1926 1927 1928 1929 1930 1931 joOURE g-The aerage numher 01 lambs horn alive per 1110 ewes bred (nlllnboulllets and Corriedalesl In

relation to the seasonal precipitatfon (Apr I to Sept 30) 01 the proeedln yellr 1925-32

The Corriedale group were in general more productive and the range of varifltions from year to year was much smaller Difference in percent of ewes with lamb was 888 of lambs dropped ]759 and of lambs dropped alive 1921 The high years for the firstmiddot two items were 1930 and 1931 and the high year for lambs dropped alive was 1926 The low yel1r for Iambs dropped alive by both breeds was 1929

When the number of lambs horn and the number born alive per 100 (wes bred are compared with April to September precipitatIOn

I

JNFLUEXCE OF GRAZING ON SPIUNG-FAJ~L SHEBP RANGB 21

records (fig 9) it is noted that the lamb crop fluctuated from year to to vear closely in accordance with variations in moisture conditions which prevailed during the preceding year that is the number of lambs born alive was below average in 1925 1927 ond 1929 whereas preripitation duringeoch of the preceding yeals-1924 1926 and 1928shywas also below normal On the other hand the number of live lambs born in 1926 1928 1930 and 1931 was above average and these volues corresponded to favorable moisture conditions during each previous fall Similarly lamb production was relatively lower in 1932 than in 1931 as precipitation was lower in 1931 than in 1930 Thus it appearsthat ewes in a thrifty condition in the full nsthe result of abundant forage tend to produce more live lambs in the folshylowing spring than do ewes in a year following a poor fall

No consistent relationship appears between climate and later stages of lomb development such as pounds of guin per lamb from birth to weaning the numbers weaned per 100 ewes bred or the weaned weight of lambs and pounds of lamb produced per ewe Climate and the quantity and quality of forage on the spring-fall range undoubtedly have some effect on these phases of lamb production but it is obscured by other factors such as denth due to predators disease and straying slow development due to inferior breeding mothering and methods of handling and conditions on the summer range where the lambs motured (1)

Otber important aspects of range-sheep production including yields of wool and death losses varied from year to year during the period of study partly in response to climate and forage production but the presence of other factors precluded isolation and evaluation of the specific influence of climatie factors

GRAZING INFLUENCES

The important bearing that climate has on the growth and developshyment of forage from year to year on spring-fall mnge must be undershystood and be given careful consideration in establishing periods of use and a basic rate of stocking but thnt alone is not enough The influence of good years and bad years is a serious matter but the stark necessity of anticipating such climatic variations is not conshyvincingly apparent until studies have been carried further and have revealed the effect of time and intensity of grazin~ upon the range in years of drought and years of plenty Such studIeS of grazing influshyences make it dear that overgmzing may result in range depletion of n far more lasting and serious character than any temporary declines in productivity normally induced by drought alone (pI 2) The degree to which the sagebrush-bunchgrass type of spring-fall range land can be damaged by overgrazing in a relatively short period of years is shown in the results presented iTt the following pages These results were obtained from the four 8lJ-acre paddocks designated 2 3 8 and 7 nlready described Each paddock was utilized to different degrees and for different periods in the spring followed in each case by the removal of nearly all of the reml1imng forage in the full At the same time paddock 1 gll1zed only in the fall was held I1S a check area to show the maximum improvement that mightbave been expected under vrevailing climatic conditions during the period of the study

22 TECHNICAL BULLETIN 600 U S DEPT OJ AGRlCULTUng

RANGE DEPLETION RESULTING ROM HEAVY CONTINUOUS SPRING AND LAfE FALL GRAZING

The degree to which sugebrush-bunchgmss spring-full lILuge in Idaho can be depleted by heavy continuous spring and late fl111 grazing is illustrated by results obtained during the period 1924-32 on padshydock 2 Here approximlltely 68 percent of all available foruge WIIS utilized in the spring starting when grasses reached 2-inch height growth and ending at the close of the spring gmzing sellson nnd 25 percent was consumed in the fnll leaving on the average only 7 percent of the fomge unutilized (table 9)

TAHI~E fJ-Ltduol lise under hCUlI1f cOllti7L1111~ ~JiTing all(i l(lc fall graziny of 71arldock 2 1924-82

----------fI-Jr-iII-t~g-rll-1i-n-g --~Ii ---~-u-lI-gr-II-7i-rlh-middot---I-)-O-Ilr-I~-t-ot-n-I-E-S-ll-

1_____-___-__ - -------- t _-----_1 matedI middotmiddotmiddotmiddot-i--( totlll

Yonr 1001 JM I teol jltormiddot tool Formiddot lorage

Period oIuso n~n Plriuri or U$(~ n~c ago producshyrtlllgu u5ltJd mnge used runge used t10n 1

1- - ~~~~ j~~~ -- S~~V -- 8g~~ 1Jcr Prrmiddot per Per- 1Ja Permiddot per

IQ2L iAJ1r2o-May~1 ~~~~t cr~b O(IrX13 ~f~~ ce~~ ~g~82 a9~ a~ti~8u 1I2r _j Apr H-lllllC 15 i 112 12 72 (jet Jr-XO 111 2465 28 86117 JOO 8697 HI26 bullbull Apr J7-1Ilny27 I 17RO 115 KI IO-X 2() ]18 1 I08 08 3U78 1IJ27 pr10-Jlllloll 2middot142 66 Oct20-K(Ii 12A8 14 l090 100 36110 1928 bull Apr 2-Iuoo 8 2middot1 02 7(1 Olt 26-De(middot I 60a 21lJ 55 100 31 5r 1920 jIIln-JUIlO J2 lK i1 I 74 Oet 31-Ko I middot1 85 IU ~gtj 8 13 2535 lao AprbullbullW-IUIIO l~ 8(I~ ~~ No 5-0 Hi 6 ~6 ~n 111 O~ 116O 1931 Aprbullbull9-Iunc 1_ 10bull11 f NQ 2-No It 40 ao 1527 9 1514 193L f May I-Aug 0 li92 fl5 Ko Hromiddot 0 l3fJ 10 21 ~I 05 32 i8 ----- -~-~------

Acrage bullbull iApr25-Juno15 256[1 ~SIOCt2q-~Hi_ ~~j_a5161 ial 3i81

t EstiIIIllled [olal rllrn~o productloD (~hllpmiddotdIlYs plr Il(middotn) uverago 102middot1-25 O~l3 11)11-322middot120 Loss III lora~o vnluo hetween 1024-25 und 1031-a2 r) percent

(Oomputed average Sec loolnoto 4 p G

The rcspeeth-e tlYcruges for 1924-25 und 1931-82 and the difference in percent between them shown nt the bottom of table D are highly significnnt Sinee 1924 wns a very poor growth year while 1()25 was very good the uvcruge numbcr of sheep-duys of feed per ncre proshyduced in these 2 years is considered to be a reliable index of the proshyductivity of the pasture at the start of the grazing tests Similurly 1931 and 1932 were rclatively poor and good yeals rcspectivelYi hence the avernge of these 2 years is considered a fair index of the productivity of the nreH ut the end of the test period

Under this system und intensity of grazing the number of sheepshyduys of feed fluctuated about in accordance with growing conditions on the runge during the first 2 years of the study After the excepshytionolly good growth yeur of 1925 however und in spite of fairly fa orable growing conditions in 1927 und ] 929 the productivity of the posture deelined consistently to the low level of less thun 16 sheepshydays of fecd per uere in 1931 (fig 10) As the result of better-thanshyoverage growing conditions in 1932 n little more than twice as much Iornge was proclueed in that yenr but the uvernge of feed produeed in these lnst 2 yenrs wns 65 PlTCll1t less than the nverage of the first 2 yoals of the study

Coinei(cntaJ with the dedinl in the sheep-days of feed produced sigllificant changes occurred ill tho vegetative covcr (pI 3) Acshy

20 TECHNICAL BULLETIN 600 U S DEPT OF AGRIOULTURE

For Rambouillets the average of 1699 percent of ewes not with lamb included all drys and all ewes dead or missing from breeding to lambing Percent of ewes with lamb varied by 1869 from 1929 to 1930 The number of Rambouillet lambs dropped per 100 ewes bred varied by 3158 and those dropped alive by 3327 between 1929 and 1931

LIVE LAMBS DROPPED PER 100 EWES 8RED

DEPARTURE FROM 8-YEAR AVERAGE

~

Ishy---

CJ l-

I I L---I AVERAGE 8901

--shy

-shy

16 1925 1926 1927 1928 1929 1930 1931 1932

12

SEASONAL PRECIPITATION OF PRECEDING YEAR-

~ --~I- Ishy -r--shy

--- - - I- r- - -I Jo

1924 1925 1926 1927 1928 1929 1930 1931 joOURE g-The aerage numher 01 lambs horn alive per 1110 ewes bred (nlllnboulllets and Corriedalesl In

relation to the seasonal precipitatfon (Apr I to Sept 30) 01 the proeedln yellr 1925-32

The Corriedale group were in general more productive and the range of varifltions from year to year was much smaller Difference in percent of ewes with lamb was 888 of lambs dropped ]759 and of lambs dropped alive 1921 The high years for the firstmiddot two items were 1930 and 1931 and the high year for lambs dropped alive was 1926 The low yel1r for Iambs dropped alive by both breeds was 1929

When the number of lambs horn and the number born alive per 100 (wes bred are compared with April to September precipitatIOn

I

JNFLUEXCE OF GRAZING ON SPIUNG-FAJ~L SHEBP RANGB 21

records (fig 9) it is noted that the lamb crop fluctuated from year to to vear closely in accordance with variations in moisture conditions which prevailed during the preceding year that is the number of lambs born alive was below average in 1925 1927 ond 1929 whereas preripitation duringeoch of the preceding yeals-1924 1926 and 1928shywas also below normal On the other hand the number of live lambs born in 1926 1928 1930 and 1931 was above average and these volues corresponded to favorable moisture conditions during each previous fall Similarly lamb production was relatively lower in 1932 than in 1931 as precipitation was lower in 1931 than in 1930 Thus it appearsthat ewes in a thrifty condition in the full nsthe result of abundant forage tend to produce more live lambs in the folshylowing spring than do ewes in a year following a poor fall

No consistent relationship appears between climate and later stages of lomb development such as pounds of guin per lamb from birth to weaning the numbers weaned per 100 ewes bred or the weaned weight of lambs and pounds of lamb produced per ewe Climate and the quantity and quality of forage on the spring-fall range undoubtedly have some effect on these phases of lamb production but it is obscured by other factors such as denth due to predators disease and straying slow development due to inferior breeding mothering and methods of handling and conditions on the summer range where the lambs motured (1)

Otber important aspects of range-sheep production including yields of wool and death losses varied from year to year during the period of study partly in response to climate and forage production but the presence of other factors precluded isolation and evaluation of the specific influence of climatie factors

GRAZING INFLUENCES

The important bearing that climate has on the growth and developshyment of forage from year to year on spring-fall mnge must be undershystood and be given careful consideration in establishing periods of use and a basic rate of stocking but thnt alone is not enough The influence of good years and bad years is a serious matter but the stark necessity of anticipating such climatic variations is not conshyvincingly apparent until studies have been carried further and have revealed the effect of time and intensity of grazin~ upon the range in years of drought and years of plenty Such studIeS of grazing influshyences make it dear that overgmzing may result in range depletion of n far more lasting and serious character than any temporary declines in productivity normally induced by drought alone (pI 2) The degree to which the sagebrush-bunchgrass type of spring-fall range land can be damaged by overgrazing in a relatively short period of years is shown in the results presented iTt the following pages These results were obtained from the four 8lJ-acre paddocks designated 2 3 8 and 7 nlready described Each paddock was utilized to different degrees and for different periods in the spring followed in each case by the removal of nearly all of the reml1imng forage in the full At the same time paddock 1 gll1zed only in the fall was held I1S a check area to show the maximum improvement that mightbave been expected under vrevailing climatic conditions during the period of the study

22 TECHNICAL BULLETIN 600 U S DEPT OJ AGRlCULTUng

RANGE DEPLETION RESULTING ROM HEAVY CONTINUOUS SPRING AND LAfE FALL GRAZING

The degree to which sugebrush-bunchgmss spring-full lILuge in Idaho can be depleted by heavy continuous spring and late fl111 grazing is illustrated by results obtained during the period 1924-32 on padshydock 2 Here approximlltely 68 percent of all available foruge WIIS utilized in the spring starting when grasses reached 2-inch height growth and ending at the close of the spring gmzing sellson nnd 25 percent was consumed in the fnll leaving on the average only 7 percent of the fomge unutilized (table 9)

TAHI~E fJ-Ltduol lise under hCUlI1f cOllti7L1111~ ~JiTing all(i l(lc fall graziny of 71arldock 2 1924-82

----------fI-Jr-iII-t~g-rll-1i-n-g --~Ii ---~-u-lI-gr-II-7i-rlh-middot---I-)-O-Ilr-I~-t-ot-n-I-E-S-ll-

1_____-___-__ - -------- t _-----_1 matedI middotmiddotmiddotmiddot-i--( totlll

Yonr 1001 JM I teol jltormiddot tool Formiddot lorage

Period oIuso n~n Plriuri or U$(~ n~c ago producshyrtlllgu u5ltJd mnge used runge used t10n 1

1- - ~~~~ j~~~ -- S~~V -- 8g~~ 1Jcr Prrmiddot per Per- 1Ja Permiddot per

IQ2L iAJ1r2o-May~1 ~~~~t cr~b O(IrX13 ~f~~ ce~~ ~g~82 a9~ a~ti~8u 1I2r _j Apr H-lllllC 15 i 112 12 72 (jet Jr-XO 111 2465 28 86117 JOO 8697 HI26 bullbull Apr J7-1Ilny27 I 17RO 115 KI IO-X 2() ]18 1 I08 08 3U78 1IJ27 pr10-Jlllloll 2middot142 66 Oct20-K(Ii 12A8 14 l090 100 36110 1928 bull Apr 2-Iuoo 8 2middot1 02 7(1 Olt 26-De(middot I 60a 21lJ 55 100 31 5r 1920 jIIln-JUIlO J2 lK i1 I 74 Oet 31-Ko I middot1 85 IU ~gtj 8 13 2535 lao AprbullbullW-IUIIO l~ 8(I~ ~~ No 5-0 Hi 6 ~6 ~n 111 O~ 116O 1931 Aprbullbull9-Iunc 1_ 10bull11 f NQ 2-No It 40 ao 1527 9 1514 193L f May I-Aug 0 li92 fl5 Ko Hromiddot 0 l3fJ 10 21 ~I 05 32 i8 ----- -~-~------

Acrage bullbull iApr25-Juno15 256[1 ~SIOCt2q-~Hi_ ~~j_a5161 ial 3i81

t EstiIIIllled [olal rllrn~o productloD (~hllpmiddotdIlYs plr Il(middotn) uverago 102middot1-25 O~l3 11)11-322middot120 Loss III lora~o vnluo hetween 1024-25 und 1031-a2 r) percent

(Oomputed average Sec loolnoto 4 p G

The rcspeeth-e tlYcruges for 1924-25 und 1931-82 and the difference in percent between them shown nt the bottom of table D are highly significnnt Sinee 1924 wns a very poor growth year while 1()25 was very good the uvcruge numbcr of sheep-duys of feed per ncre proshyduced in these 2 years is considered to be a reliable index of the proshyductivity of the pasture at the start of the grazing tests Similurly 1931 and 1932 were rclatively poor and good yeals rcspectivelYi hence the avernge of these 2 years is considered a fair index of the productivity of the nreH ut the end of the test period

Under this system und intensity of grazing the number of sheepshyduys of feed fluctuated about in accordance with growing conditions on the runge during the first 2 years of the study After the excepshytionolly good growth yeur of 1925 however und in spite of fairly fa orable growing conditions in 1927 und ] 929 the productivity of the posture deelined consistently to the low level of less thun 16 sheepshydays of fecd per uere in 1931 (fig 10) As the result of better-thanshyoverage growing conditions in 1932 n little more than twice as much Iornge was proclueed in that yenr but the uvernge of feed produeed in these lnst 2 yenrs wns 65 PlTCll1t less than the nverage of the first 2 yoals of the study

Coinei(cntaJ with the dedinl in the sheep-days of feed produced sigllificant changes occurred ill tho vegetative covcr (pI 3) Acshy

JNFLUEXCE OF GRAZING ON SPIUNG-FAJ~L SHEBP RANGB 21

records (fig 9) it is noted that the lamb crop fluctuated from year to to vear closely in accordance with variations in moisture conditions which prevailed during the preceding year that is the number of lambs born alive was below average in 1925 1927 ond 1929 whereas preripitation duringeoch of the preceding yeals-1924 1926 and 1928shywas also below normal On the other hand the number of live lambs born in 1926 1928 1930 and 1931 was above average and these volues corresponded to favorable moisture conditions during each previous fall Similarly lamb production was relatively lower in 1932 than in 1931 as precipitation was lower in 1931 than in 1930 Thus it appearsthat ewes in a thrifty condition in the full nsthe result of abundant forage tend to produce more live lambs in the folshylowing spring than do ewes in a year following a poor fall

No consistent relationship appears between climate and later stages of lomb development such as pounds of guin per lamb from birth to weaning the numbers weaned per 100 ewes bred or the weaned weight of lambs and pounds of lamb produced per ewe Climate and the quantity and quality of forage on the spring-fall range undoubtedly have some effect on these phases of lamb production but it is obscured by other factors such as denth due to predators disease and straying slow development due to inferior breeding mothering and methods of handling and conditions on the summer range where the lambs motured (1)

Otber important aspects of range-sheep production including yields of wool and death losses varied from year to year during the period of study partly in response to climate and forage production but the presence of other factors precluded isolation and evaluation of the specific influence of climatie factors

GRAZING INFLUENCES

The important bearing that climate has on the growth and developshyment of forage from year to year on spring-fall mnge must be undershystood and be given careful consideration in establishing periods of use and a basic rate of stocking but thnt alone is not enough The influence of good years and bad years is a serious matter but the stark necessity of anticipating such climatic variations is not conshyvincingly apparent until studies have been carried further and have revealed the effect of time and intensity of grazin~ upon the range in years of drought and years of plenty Such studIeS of grazing influshyences make it dear that overgmzing may result in range depletion of n far more lasting and serious character than any temporary declines in productivity normally induced by drought alone (pI 2) The degree to which the sagebrush-bunchgrass type of spring-fall range land can be damaged by overgrazing in a relatively short period of years is shown in the results presented iTt the following pages These results were obtained from the four 8lJ-acre paddocks designated 2 3 8 and 7 nlready described Each paddock was utilized to different degrees and for different periods in the spring followed in each case by the removal of nearly all of the reml1imng forage in the full At the same time paddock 1 gll1zed only in the fall was held I1S a check area to show the maximum improvement that mightbave been expected under vrevailing climatic conditions during the period of the study

22 TECHNICAL BULLETIN 600 U S DEPT OJ AGRlCULTUng

RANGE DEPLETION RESULTING ROM HEAVY CONTINUOUS SPRING AND LAfE FALL GRAZING

The degree to which sugebrush-bunchgmss spring-full lILuge in Idaho can be depleted by heavy continuous spring and late fl111 grazing is illustrated by results obtained during the period 1924-32 on padshydock 2 Here approximlltely 68 percent of all available foruge WIIS utilized in the spring starting when grasses reached 2-inch height growth and ending at the close of the spring gmzing sellson nnd 25 percent was consumed in the fnll leaving on the average only 7 percent of the fomge unutilized (table 9)

TAHI~E fJ-Ltduol lise under hCUlI1f cOllti7L1111~ ~JiTing all(i l(lc fall graziny of 71arldock 2 1924-82

----------fI-Jr-iII-t~g-rll-1i-n-g --~Ii ---~-u-lI-gr-II-7i-rlh-middot---I-)-O-Ilr-I~-t-ot-n-I-E-S-ll-

1_____-___-__ - -------- t _-----_1 matedI middotmiddotmiddotmiddot-i--( totlll

Yonr 1001 JM I teol jltormiddot tool Formiddot lorage

Period oIuso n~n Plriuri or U$(~ n~c ago producshyrtlllgu u5ltJd mnge used runge used t10n 1

1- - ~~~~ j~~~ -- S~~V -- 8g~~ 1Jcr Prrmiddot per Per- 1Ja Permiddot per

IQ2L iAJ1r2o-May~1 ~~~~t cr~b O(IrX13 ~f~~ ce~~ ~g~82 a9~ a~ti~8u 1I2r _j Apr H-lllllC 15 i 112 12 72 (jet Jr-XO 111 2465 28 86117 JOO 8697 HI26 bullbull Apr J7-1Ilny27 I 17RO 115 KI IO-X 2() ]18 1 I08 08 3U78 1IJ27 pr10-Jlllloll 2middot142 66 Oct20-K(Ii 12A8 14 l090 100 36110 1928 bull Apr 2-Iuoo 8 2middot1 02 7(1 Olt 26-De(middot I 60a 21lJ 55 100 31 5r 1920 jIIln-JUIlO J2 lK i1 I 74 Oet 31-Ko I middot1 85 IU ~gtj 8 13 2535 lao AprbullbullW-IUIIO l~ 8(I~ ~~ No 5-0 Hi 6 ~6 ~n 111 O~ 116O 1931 Aprbullbull9-Iunc 1_ 10bull11 f NQ 2-No It 40 ao 1527 9 1514 193L f May I-Aug 0 li92 fl5 Ko Hromiddot 0 l3fJ 10 21 ~I 05 32 i8 ----- -~-~------

Acrage bullbull iApr25-Juno15 256[1 ~SIOCt2q-~Hi_ ~~j_a5161 ial 3i81

t EstiIIIllled [olal rllrn~o productloD (~hllpmiddotdIlYs plr Il(middotn) uverago 102middot1-25 O~l3 11)11-322middot120 Loss III lora~o vnluo hetween 1024-25 und 1031-a2 r) percent

(Oomputed average Sec loolnoto 4 p G

The rcspeeth-e tlYcruges for 1924-25 und 1931-82 and the difference in percent between them shown nt the bottom of table D are highly significnnt Sinee 1924 wns a very poor growth year while 1()25 was very good the uvcruge numbcr of sheep-duys of feed per ncre proshyduced in these 2 years is considered to be a reliable index of the proshyductivity of the pasture at the start of the grazing tests Similurly 1931 and 1932 were rclatively poor and good yeals rcspectivelYi hence the avernge of these 2 years is considered a fair index of the productivity of the nreH ut the end of the test period

Under this system und intensity of grazing the number of sheepshyduys of feed fluctuated about in accordance with growing conditions on the runge during the first 2 years of the study After the excepshytionolly good growth yeur of 1925 however und in spite of fairly fa orable growing conditions in 1927 und ] 929 the productivity of the posture deelined consistently to the low level of less thun 16 sheepshydays of fecd per uere in 1931 (fig 10) As the result of better-thanshyoverage growing conditions in 1932 n little more than twice as much Iornge was proclueed in that yenr but the uvernge of feed produeed in these lnst 2 yenrs wns 65 PlTCll1t less than the nverage of the first 2 yoals of the study

Coinei(cntaJ with the dedinl in the sheep-days of feed produced sigllificant changes occurred ill tho vegetative covcr (pI 3) Acshy

22 TECHNICAL BULLETIN 600 U S DEPT OJ AGRlCULTUng

RANGE DEPLETION RESULTING ROM HEAVY CONTINUOUS SPRING AND LAfE FALL GRAZING

The degree to which sugebrush-bunchgmss spring-full lILuge in Idaho can be depleted by heavy continuous spring and late fl111 grazing is illustrated by results obtained during the period 1924-32 on padshydock 2 Here approximlltely 68 percent of all available foruge WIIS utilized in the spring starting when grasses reached 2-inch height growth and ending at the close of the spring gmzing sellson nnd 25 percent was consumed in the fnll leaving on the average only 7 percent of the fomge unutilized (table 9)

TAHI~E fJ-Ltduol lise under hCUlI1f cOllti7L1111~ ~JiTing all(i l(lc fall graziny of 71arldock 2 1924-82

----------fI-Jr-iII-t~g-rll-1i-n-g --~Ii ---~-u-lI-gr-II-7i-rlh-middot---I-)-O-Ilr-I~-t-ot-n-I-E-S-ll-

1_____-___-__ - -------- t _-----_1 matedI middotmiddotmiddotmiddot-i--( totlll

Yonr 1001 JM I teol jltormiddot tool Formiddot lorage

Period oIuso n~n Plriuri or U$(~ n~c ago producshyrtlllgu u5ltJd mnge used runge used t10n 1

1- - ~~~~ j~~~ -- S~~V -- 8g~~ 1Jcr Prrmiddot per Per- 1Ja Permiddot per

IQ2L iAJ1r2o-May~1 ~~~~t cr~b O(IrX13 ~f~~ ce~~ ~g~82 a9~ a~ti~8u 1I2r _j Apr H-lllllC 15 i 112 12 72 (jet Jr-XO 111 2465 28 86117 JOO 8697 HI26 bullbull Apr J7-1Ilny27 I 17RO 115 KI IO-X 2() ]18 1 I08 08 3U78 1IJ27 pr10-Jlllloll 2middot142 66 Oct20-K(Ii 12A8 14 l090 100 36110 1928 bull Apr 2-Iuoo 8 2middot1 02 7(1 Olt 26-De(middot I 60a 21lJ 55 100 31 5r 1920 jIIln-JUIlO J2 lK i1 I 74 Oet 31-Ko I middot1 85 IU ~gtj 8 13 2535 lao AprbullbullW-IUIIO l~ 8(I~ ~~ No 5-0 Hi 6 ~6 ~n 111 O~ 116O 1931 Aprbullbull9-Iunc 1_ 10bull11 f NQ 2-No It 40 ao 1527 9 1514 193L f May I-Aug 0 li92 fl5 Ko Hromiddot 0 l3fJ 10 21 ~I 05 32 i8 ----- -~-~------

Acrage bullbull iApr25-Juno15 256[1 ~SIOCt2q-~Hi_ ~~j_a5161 ial 3i81

t EstiIIIllled [olal rllrn~o productloD (~hllpmiddotdIlYs plr Il(middotn) uverago 102middot1-25 O~l3 11)11-322middot120 Loss III lora~o vnluo hetween 1024-25 und 1031-a2 r) percent

(Oomputed average Sec loolnoto 4 p G

The rcspeeth-e tlYcruges for 1924-25 und 1931-82 and the difference in percent between them shown nt the bottom of table D are highly significnnt Sinee 1924 wns a very poor growth year while 1()25 was very good the uvcruge numbcr of sheep-duys of feed per ncre proshyduced in these 2 years is considered to be a reliable index of the proshyductivity of the pasture at the start of the grazing tests Similurly 1931 and 1932 were rclatively poor and good yeals rcspectivelYi hence the avernge of these 2 years is considered a fair index of the productivity of the nreH ut the end of the test period

Under this system und intensity of grazing the number of sheepshyduys of feed fluctuated about in accordance with growing conditions on the runge during the first 2 years of the study After the excepshytionolly good growth yeur of 1925 however und in spite of fairly fa orable growing conditions in 1927 und ] 929 the productivity of the posture deelined consistently to the low level of less thun 16 sheepshydays of fecd per uere in 1931 (fig 10) As the result of better-thanshyoverage growing conditions in 1932 n little more than twice as much Iornge was proclueed in that yenr but the uvernge of feed produeed in these lnst 2 yenrs wns 65 PlTCll1t less than the nverage of the first 2 yoals of the study

Coinei(cntaJ with the dedinl in the sheep-days of feed produced sigllificant changes occurred ill tho vegetative covcr (pI 3) Acshy

Technicll3ullctin 600 U S Dept 01 Agriculture PLATE 2

Technical Hullctin (00 U S Dept of Agriculture PLATE 3

Fl 1194 217843

OVERGRAZING DESROYS CONSERVATIVE GRAZING BUILDS UP

Ilensity of th~ nhllinly unlJlllntnhl~ Mlnhrush is itltrI(ISit1 II) too ht U( o[ hlJn~h)r~I nnd w(pls (lt1) untl rnlll) lorullt tlWfllIPOIl 1H(oliu OIlhh~i for fUJlllmiddotmiddotshlmiddot(jJ prOdlitHlil HnJlgt in this (OJlf Ii I ion nrc very JU- in ((rrSin~ (fll)fl(it~ 11Il1h~ art~ lost (rolll slrti~middotil)J HJllf 1I111lI1 Hoi is IHJ1Il(j fnull tlw ~id(s und h~IIiIs or Ihe slt((middotI (onid~rnI~ lo illl( I iIb Oil Ill( nlhl hIIII llltrt thlgt Yllhlllhiu hunch~TlIsses lire [lrl)((ur hy (olls(nuti( ~rljll)( (ill Ihr will lIot ollly hllilltl lIJl good w(i~hls III the ewes IIIHI jnslJr( )O(uJ Jam)) (mJl~ hili illJld1lI1mllh(gt WIll hlIIgtI- III mult ~11middotsrllllmiddot wilh thl Jess tleslrlhll sng(Imlgth UII klepll 1101111 011 Ihe sllg(hruslr plunt kiIJ(lt1 IIul iUlhe Ti~hl rUTj(roUIII

--------- ----------

------------------

INJLUENCE OJ GRAZING 0)1 SPRING-FALL SHEEP RANGE 23

cording to ocular estimates of the vegetation over the area as a whole the density of the highly palatable grasses and weeds decreased 67 and 81 percent respectively between 1924 and 1930 (table 10)

The losses in these two claEes of forage were confined principally to the wheatgrasses needlegrasses and bluegrasses and to such choice weed plants as the crepis and balsamroot which were either killed or reduced in size On the other hand the density of the relashytively unpalatable shrubs principally sagebrush increased by nearly three-fourths in the sume 6 years partly through the establishment of

FIGURE JO-Trcnd In estimated total annual forn~e production under heavy continuous sprin~ grazIng and lute fall use 1924-32

TABLE lO-Effect of hla~Y continuolts 87Jring and lale fall grazing on paddock 2 as shown bll the relatite composition and ground cover of the vegetation in 1924shyand 1980

Area of paddock coverell by vegetatlon Composition of

of cover Class of forage 1otal cover Palutable cover

1924 1930 1924 1930 Change 1921 1930 Change

Pacwt Pacent Percent PTcent Percent Pacwl Pacent Pacont Drowse 4004 81 26 11 62 2012 +i3 1 24 14i +19 Grass_bullbullbullbull_ aOlo 1385 11 34 343 -iO i94 262 -ui 100lt15__bullbullbullbullbull_bullbullbullbullbullbull_ 2086 489 606 1 20 -80 213 55 -81

TotaL 100 00 2902 24 i5 -15 121l middot164 -62lOiiOOl

new plants and partly by vigorous expansion of the crowns of old ones (fig 11) Although the increase in the grgtwth of sagebrush and other shrubs tended to compensate for the losses of grasses and weeds in the stand the total density of the cover in 1930 was about 15 percent less than in 1924

Further indication of the manner in which such heavy grazing reshyduced the forage value of this range was gnined from t1 comparison for the years 1923-32 of the bast11 aret1 of perennial grasses on a me telshysquare quadrat laid out on a portion of this paddock that was fairly representative of the area as a whole As may be seen from table 11

24 TECHNICAL BULLETIN 600 U S DEPT OF AGltICULTURE

the decrease in basal area for the entire period was 92 percent The weakening effects of this character of grazin~ is illustrated also by the declining vigor of the herbaceous vegetatIOn to the degree that

during the last 4 years of the grazing period

_ PALATABLE VEGETATION the development of thecJ UNPALATABLE VEGETATION herbltceous vegetation to 2-inch height growth lagged from 2 to 14 days behind the time when similar plants on less heavily grazed range reached thi s stage RLlldom measurements of height growth and flower-stalk counts conshyfirmed these evidences Bnlsumroot plants on

1924 1930 this area produced anshy

FIGURE ll-Elfect of heavy continuous sprln~ and late faUuse on the palatability of rango coer hot ween 11)24 and JU30 nually only one or two

flower stalks from 4 to 5 inches in length per plant whereas 12 to 15 flower stalks 12 to 20 inches in length were produced on balsamroot plants nearby under moderate grazing

TAnIE ll-The shrinkage in basal area of perennial grasses on a representative meter quadrat in paddock 2 and the lag in rCUlUne~s for grazing (2-inch height growth) as compared to protected ranye

Lag Innusal lag In I IBasal ILag In DasalYenrs ur~u rcadlmiddot Yenrs urell rcadlmiddot Years urea readlmiddot

I ness

_ ___ I nessness ----I ----middot------11-----middot1---shy

(III ])fIV 1 (m naVamp Cm ]Java 80 ())021J bullbull bull bull 108 2 Hla2~~~~H~ al 14 727 U 10aU _ 1) 7 ----shy321 Il 1111 127 n 1 Shrlllkug 355 bullbullbullbullbullbullbullbull I

Furthermore observations maue within a Tod-square portion of this range which WitS protected from grazing in 1930 and 1931 revealed that the balsamroot and other wenJwned pnlntable pI nn ts failed to show any n ppreciable return in vigoL by the end of the spring growing suason in 1931 in spite of the fact that growing conditions were nearly nOlmal in these years Thus it nppeurs that when sagebrush-bullchgrass range of this chamcter is seriously depIcted it will require several years to restore the normal vigor of the rel11nining desirable fornge plants and undoubtedly mnny more years of protection or a combination of protection and Ycry conservative grnzing before new plants will take the place of those killed

The decline in the productivity of this range area is comparable to the depIcted conditiol1 of extensive areas of spring-fall range lands in southeastern Iunho on which grazing is uncontlmiddotolled One band of sheep follows another on the range in the spring utilizing a large percentage of the forage as rnpidly as it is produced In mnny instanees the same ranges nrc ngnin gmzed very heltvily in the fall Such utilization has no pln(c in good mnge mnnngement

----------

----- -------------

INFLUENCE OF GRAZING ON SPRING-JALL SHEEP RANG1~ 25

DEPLETION FROM HEAVY EARLY SPRING AND LATE FALl GRAZING

Several years of early spring grazing repeated at approximately the same period of plant growth each year and followed by fall grazin~ may also be detrimental to sagebrush-bunchgrass range This IS evident in the results of grazing tests in paddock 3 during the years 1924-32 A summary of these tests ill table 12 shows that 36 percent

FIGURE 12-Trend in estimated total annual forage production under heavy early spring and heavy fall use of the range 1024-32

of the forage was utilized on the average in ~1 4-week period each spring starting after grasses reached 2-inch height growth A somewhat larger percent (46) was removed in the fall npresenting a total annual utilization of 82 percent

TABLE 12-Actual use under heavy early spring and late fall grazing of paddock 3 1924-32

Spring grazing Fall grllzing Yearly total Estimiddot mated totalYear For- Formiddot Formiddot forageU~e of Use of Use ofPeriod of use age Period of use age age producmiddotrango range rungoused used used tion I

Sheepmiddot SheeP Sheepmiddot Sheepmiddotdava dllVa davs dav per Permiddot per Permiddot per Permiddot perClert cent acre Ce1lt acre cent acre

1924bullbullbullbull _bullbull Apr 23-Mny 29_ 19 26 34 Oct 5-Nov 13bullbullbull 2814 50 4740 84 5643 1925bullbullbullbullbullbullbullbull AprlJ-MIlY 10 bull 2744 31 Oct Il-Nov 24 5426 iii 8170 92 8880 1926bull_bullbullbullbull Apr 17-MIlY 10bullbull 2997 54 0lt15-Nov2IL 1715 JI 4712 85 65441927___ bull ___ bull Apr 29-MIlY 31 1470 30 Oct 2O-Nov 29__ 2974 00 4444 00 49381928_________ Apr 26-Mny 19__ 1828 52 Oct 20-Dec L__ 1525 43 3353 95 35291029______ MayO-lvrlly2U 881 3U Nov 12-Nov 27 1032 (17 2813 97 2900loao ________ AprIO-JuneLbull 057 45 Nov 5-Nov HI __ 040 31 Iii 03 76 2100 193L___bull Apr 3U-May 21 1217 34 Nov 2-Nov 25 bullbull 1a80 38 297 72 36071932_______bull May i-June L __ bull 9aO 25 Nov I-Nov 12__ 788 21 1718 46 37a5

Average Apr 25-May 2J_ 1061 ao Oct 25-No 22__ 2133 40 3794 82 bull 46 27

I Estlmated totnl forage production (sheepmiddotdnys per acre) average 1924-25 7262 1931-32 3671 Loss in Cornge value between 11124-25 and 1931-32 49 percent

bull Computed averages Seo footnote 4 p O

26 TECHNICAL BULLETIN 600 U S DEPT OF AGRICULTURE

This area produced un estimated wemge of 73 sheep-days of feed per acre in the first 2 years of the experiment But here as in other paddocks heavily gmzed in the spring enrly forage production declined consistently to a low leyel by the end of the period (fig 12) The average of the 2 years 1931 and 1932 was ouly 37 sheep-days or nearly 50 percent less than the average of the first 2 years Although this was an improvement oyer the preceding 2 years attributable to the more fayorable growing conditions in 1932 it did not tfled materially the definite downward trend for the period as a wbole

As under heayy continuous spring grazing in paddock 2 this conshysiderable decline in ayailable forage resulted in a very sigllificant change in the composition and hence in the palatability of tho vegetashytion as shown in table 13 und figure 13 In 1924 grass and browse

coverednearly eq ual porshy_ PALATABLE tions of the paddock butVEGETATION

i cJ UNPALATABLE VEGETATION by 1930 the density of sect16r -------------------4 shrubs increased more 5 than 50 percent and ~ covered about three and12~----------------__4

one-half times the grass area Most of this inshycrease was due to the expansion of the size of sagebrush and other relatively unpnlntable shrubs rhe reduction in density of the grasses

1930 by more than 50 percent FIGlltE 13-ElTecl of hClIY cllrly spring lind late filII grazing OIl and that of the weeds bv

pnilltubility of range covor between JU24 and 1D30 18 perceni ([e Inrgely

due to the destruction of the most desirable forage plants such as wheatgrass bluegrass clepis and balsarnroot 110reorcr ns is evishydent in table 141 the baslLl UJca of pcrennial gmsses Oil lL metershysquare quadrat decreased between 1926 and 1932 by 77 pereent

In addition to these ~ross changes in the plant cover table 14 revenls a measurable decrease ill the vigor of the herbaceous plants during the last 4 years of the study period Two-inch-height growth was not attained on this area until 6 to 10 days after the same stage of developshyment was reached on more consefTatively grazed adjacent range Moreover flower stalks on the bnlsamroot plants were neither so numerous nor so long-stemmed as those on protected range

TABLE 13-Effect of heatmiddoty early slJring and laic fall grazing on paddork 3 a shown by the relative C01lt1Josilion and ground cover oj the vegealion in 1924 and 1930

I reu of l lndduck COlr(d hy vcgctlltlon

Composition of ________-________ Class of forage cover rolal cOvtr Jlailltubll COVllr

_________ ~~~ 102middot ~ Chunge - lJ2~ I~ Chung

P~TCr71t Percent Perceltt Percent PtrCtmt IJtreeIlt Perct7lt Percent Drowsmiddotbullbullbullbullbullbullbullbull_bullbullbull 4118 MOfgt 11middot15 17fgt +51 I1S Ili2 +51 Oms ________ 1029 1877 1U811 bIIS -fia 7114 184 -[2 Wecds__ ~~ 515 ~~~~~

Tuta lUOOO HX1IKI 2769 2703 -21 1226 bullbull 2 -41

Technical Hullctin (00 U S Dept of Agriculture PLATE 3

Fl 1194 217843

OVERGRAZING DESROYS CONSERVATIVE GRAZING BUILDS UP

Ilensity of th~ nhllinly unlJlllntnhl~ Mlnhrush is itltrI(ISit1 II) too ht U( o[ hlJn~h)r~I nnd w(pls (lt1) untl rnlll) lorullt tlWfllIPOIl 1H(oliu OIlhh~i for fUJlllmiddotmiddotshlmiddot(jJ prOdlitHlil HnJlgt in this (OJlf Ii I ion nrc very JU- in ((rrSin~ (fll)fl(it~ 11Il1h~ art~ lost (rolll slrti~middotil)J HJllf 1I111lI1 Hoi is IHJ1Il(j fnull tlw ~id(s und h~IIiIs or Ihe slt((middotI (onid~rnI~ lo illl( I iIb Oil Ill( nlhl hIIII llltrt thlgt Yllhlllhiu hunch~TlIsses lire [lrl)((ur hy (olls(nuti( ~rljll)( (ill Ihr will lIot ollly hllilltl lIJl good w(i~hls III the ewes IIIHI jnslJr( )O(uJ Jam)) (mJl~ hili illJld1lI1mllh(gt WIll hlIIgtI- III mult ~11middotsrllllmiddot wilh thl Jess tleslrlhll sng(Imlgth UII klepll 1101111 011 Ihe sllg(hruslr plunt kiIJ(lt1 IIul iUlhe Ti~hl rUTj(roUIII

--------- ----------

------------------

INJLUENCE OJ GRAZING 0)1 SPRING-FALL SHEEP RANGE 23

cording to ocular estimates of the vegetation over the area as a whole the density of the highly palatable grasses and weeds decreased 67 and 81 percent respectively between 1924 and 1930 (table 10)

The losses in these two claEes of forage were confined principally to the wheatgrasses needlegrasses and bluegrasses and to such choice weed plants as the crepis and balsamroot which were either killed or reduced in size On the other hand the density of the relashytively unpalatable shrubs principally sagebrush increased by nearly three-fourths in the sume 6 years partly through the establishment of

FIGURE JO-Trcnd In estimated total annual forn~e production under heavy continuous sprin~ grazIng and lute fall use 1924-32

TABLE lO-Effect of hla~Y continuolts 87Jring and lale fall grazing on paddock 2 as shown bll the relatite composition and ground cover of the vegetation in 1924shyand 1980

Area of paddock coverell by vegetatlon Composition of

of cover Class of forage 1otal cover Palutable cover

1924 1930 1924 1930 Change 1921 1930 Change

Pacwt Pacent Percent PTcent Percent Pacwl Pacent Pacont Drowse 4004 81 26 11 62 2012 +i3 1 24 14i +19 Grass_bullbullbullbull_ aOlo 1385 11 34 343 -iO i94 262 -ui 100lt15__bullbullbullbullbull_bullbullbullbullbullbull_ 2086 489 606 1 20 -80 213 55 -81

TotaL 100 00 2902 24 i5 -15 121l middot164 -62lOiiOOl

new plants and partly by vigorous expansion of the crowns of old ones (fig 11) Although the increase in the grgtwth of sagebrush and other shrubs tended to compensate for the losses of grasses and weeds in the stand the total density of the cover in 1930 was about 15 percent less than in 1924

Further indication of the manner in which such heavy grazing reshyduced the forage value of this range was gnined from t1 comparison for the years 1923-32 of the bast11 aret1 of perennial grasses on a me telshysquare quadrat laid out on a portion of this paddock that was fairly representative of the area as a whole As may be seen from table 11

24 TECHNICAL BULLETIN 600 U S DEPT OF AGltICULTURE

the decrease in basal area for the entire period was 92 percent The weakening effects of this character of grazin~ is illustrated also by the declining vigor of the herbaceous vegetatIOn to the degree that

during the last 4 years of the grazing period

_ PALATABLE VEGETATION the development of thecJ UNPALATABLE VEGETATION herbltceous vegetation to 2-inch height growth lagged from 2 to 14 days behind the time when similar plants on less heavily grazed range reached thi s stage RLlldom measurements of height growth and flower-stalk counts conshyfirmed these evidences Bnlsumroot plants on

1924 1930 this area produced anshy

FIGURE ll-Elfect of heavy continuous sprln~ and late faUuse on the palatability of rango coer hot ween 11)24 and JU30 nually only one or two

flower stalks from 4 to 5 inches in length per plant whereas 12 to 15 flower stalks 12 to 20 inches in length were produced on balsamroot plants nearby under moderate grazing

TAnIE ll-The shrinkage in basal area of perennial grasses on a representative meter quadrat in paddock 2 and the lag in rCUlUne~s for grazing (2-inch height growth) as compared to protected ranye

Lag Innusal lag In I IBasal ILag In DasalYenrs ur~u rcadlmiddot Yenrs urell rcadlmiddot Years urea readlmiddot

I ness

_ ___ I nessness ----I ----middot------11-----middot1---shy

(III ])fIV 1 (m naVamp Cm ]Java 80 ())021J bullbull bull bull 108 2 Hla2~~~~H~ al 14 727 U 10aU _ 1) 7 ----shy321 Il 1111 127 n 1 Shrlllkug 355 bullbullbullbullbullbullbullbull I

Furthermore observations maue within a Tod-square portion of this range which WitS protected from grazing in 1930 and 1931 revealed that the balsamroot and other wenJwned pnlntable pI nn ts failed to show any n ppreciable return in vigoL by the end of the spring growing suason in 1931 in spite of the fact that growing conditions were nearly nOlmal in these years Thus it nppeurs that when sagebrush-bullchgrass range of this chamcter is seriously depIcted it will require several years to restore the normal vigor of the rel11nining desirable fornge plants and undoubtedly mnny more years of protection or a combination of protection and Ycry conservative grnzing before new plants will take the place of those killed

The decline in the productivity of this range area is comparable to the depIcted conditiol1 of extensive areas of spring-fall range lands in southeastern Iunho on which grazing is uncontlmiddotolled One band of sheep follows another on the range in the spring utilizing a large percentage of the forage as rnpidly as it is produced In mnny instanees the same ranges nrc ngnin gmzed very heltvily in the fall Such utilization has no pln(c in good mnge mnnngement

----------

----- -------------

INFLUENCE OF GRAZING ON SPRING-JALL SHEEP RANG1~ 25

DEPLETION FROM HEAVY EARLY SPRING AND LATE FALl GRAZING

Several years of early spring grazing repeated at approximately the same period of plant growth each year and followed by fall grazin~ may also be detrimental to sagebrush-bunchgrass range This IS evident in the results of grazing tests in paddock 3 during the years 1924-32 A summary of these tests ill table 12 shows that 36 percent

FIGURE 12-Trend in estimated total annual forage production under heavy early spring and heavy fall use of the range 1024-32

of the forage was utilized on the average in ~1 4-week period each spring starting after grasses reached 2-inch height growth A somewhat larger percent (46) was removed in the fall npresenting a total annual utilization of 82 percent

TABLE 12-Actual use under heavy early spring and late fall grazing of paddock 3 1924-32

Spring grazing Fall grllzing Yearly total Estimiddot mated totalYear For- Formiddot Formiddot forageU~e of Use of Use ofPeriod of use age Period of use age age producmiddotrango range rungoused used used tion I

Sheepmiddot SheeP Sheepmiddot Sheepmiddotdava dllVa davs dav per Permiddot per Permiddot per Permiddot perClert cent acre Ce1lt acre cent acre

1924bullbullbullbull _bullbull Apr 23-Mny 29_ 19 26 34 Oct 5-Nov 13bullbullbull 2814 50 4740 84 5643 1925bullbullbullbullbullbullbullbull AprlJ-MIlY 10 bull 2744 31 Oct Il-Nov 24 5426 iii 8170 92 8880 1926bull_bullbullbullbull Apr 17-MIlY 10bullbull 2997 54 0lt15-Nov2IL 1715 JI 4712 85 65441927___ bull ___ bull Apr 29-MIlY 31 1470 30 Oct 2O-Nov 29__ 2974 00 4444 00 49381928_________ Apr 26-Mny 19__ 1828 52 Oct 20-Dec L__ 1525 43 3353 95 35291029______ MayO-lvrlly2U 881 3U Nov 12-Nov 27 1032 (17 2813 97 2900loao ________ AprIO-JuneLbull 057 45 Nov 5-Nov HI __ 040 31 Iii 03 76 2100 193L___bull Apr 3U-May 21 1217 34 Nov 2-Nov 25 bullbull 1a80 38 297 72 36071932_______bull May i-June L __ bull 9aO 25 Nov I-Nov 12__ 788 21 1718 46 37a5

Average Apr 25-May 2J_ 1061 ao Oct 25-No 22__ 2133 40 3794 82 bull 46 27

I Estlmated totnl forage production (sheepmiddotdnys per acre) average 1924-25 7262 1931-32 3671 Loss in Cornge value between 11124-25 and 1931-32 49 percent

bull Computed averages Seo footnote 4 p O

26 TECHNICAL BULLETIN 600 U S DEPT OF AGRICULTURE

This area produced un estimated wemge of 73 sheep-days of feed per acre in the first 2 years of the experiment But here as in other paddocks heavily gmzed in the spring enrly forage production declined consistently to a low leyel by the end of the period (fig 12) The average of the 2 years 1931 and 1932 was ouly 37 sheep-days or nearly 50 percent less than the average of the first 2 years Although this was an improvement oyer the preceding 2 years attributable to the more fayorable growing conditions in 1932 it did not tfled materially the definite downward trend for the period as a wbole

As under heayy continuous spring grazing in paddock 2 this conshysiderable decline in ayailable forage resulted in a very sigllificant change in the composition and hence in the palatability of tho vegetashytion as shown in table 13 und figure 13 In 1924 grass and browse

coverednearly eq ual porshy_ PALATABLE tions of the paddock butVEGETATION

i cJ UNPALATABLE VEGETATION by 1930 the density of sect16r -------------------4 shrubs increased more 5 than 50 percent and ~ covered about three and12~----------------__4

one-half times the grass area Most of this inshycrease was due to the expansion of the size of sagebrush and other relatively unpnlntable shrubs rhe reduction in density of the grasses

1930 by more than 50 percent FIGlltE 13-ElTecl of hClIY cllrly spring lind late filII grazing OIl and that of the weeds bv

pnilltubility of range covor between JU24 and 1D30 18 perceni ([e Inrgely

due to the destruction of the most desirable forage plants such as wheatgrass bluegrass clepis and balsarnroot 110reorcr ns is evishydent in table 141 the baslLl UJca of pcrennial gmsses Oil lL metershysquare quadrat decreased between 1926 and 1932 by 77 pereent

In addition to these ~ross changes in the plant cover table 14 revenls a measurable decrease ill the vigor of the herbaceous plants during the last 4 years of the study period Two-inch-height growth was not attained on this area until 6 to 10 days after the same stage of developshyment was reached on more consefTatively grazed adjacent range Moreover flower stalks on the bnlsamroot plants were neither so numerous nor so long-stemmed as those on protected range

TABLE 13-Effect of heatmiddoty early slJring and laic fall grazing on paddork 3 a shown by the relative C01lt1Josilion and ground cover oj the vegealion in 1924 and 1930

I reu of l lndduck COlr(d hy vcgctlltlon

Composition of ________-________ Class of forage cover rolal cOvtr Jlailltubll COVllr

_________ ~~~ 102middot ~ Chunge - lJ2~ I~ Chung

P~TCr71t Percent Perceltt Percent PtrCtmt IJtreeIlt Perct7lt Percent Drowsmiddotbullbullbullbullbullbullbullbull_bullbullbull 4118 MOfgt 11middot15 17fgt +51 I1S Ili2 +51 Oms ________ 1029 1877 1U811 bIIS -fia 7114 184 -[2 Wecds__ ~~ 515 ~~~~~

Tuta lUOOO HX1IKI 2769 2703 -21 1226 bullbull 2 -41

--------- ----------

------------------

INJLUENCE OJ GRAZING 0)1 SPRING-FALL SHEEP RANGE 23

cording to ocular estimates of the vegetation over the area as a whole the density of the highly palatable grasses and weeds decreased 67 and 81 percent respectively between 1924 and 1930 (table 10)

The losses in these two claEes of forage were confined principally to the wheatgrasses needlegrasses and bluegrasses and to such choice weed plants as the crepis and balsamroot which were either killed or reduced in size On the other hand the density of the relashytively unpalatable shrubs principally sagebrush increased by nearly three-fourths in the sume 6 years partly through the establishment of

FIGURE JO-Trcnd In estimated total annual forn~e production under heavy continuous sprin~ grazIng and lute fall use 1924-32

TABLE lO-Effect of hla~Y continuolts 87Jring and lale fall grazing on paddock 2 as shown bll the relatite composition and ground cover of the vegetation in 1924shyand 1980

Area of paddock coverell by vegetatlon Composition of

of cover Class of forage 1otal cover Palutable cover

1924 1930 1924 1930 Change 1921 1930 Change

Pacwt Pacent Percent PTcent Percent Pacwl Pacent Pacont Drowse 4004 81 26 11 62 2012 +i3 1 24 14i +19 Grass_bullbullbullbull_ aOlo 1385 11 34 343 -iO i94 262 -ui 100lt15__bullbullbullbullbull_bullbullbullbullbullbull_ 2086 489 606 1 20 -80 213 55 -81

TotaL 100 00 2902 24 i5 -15 121l middot164 -62lOiiOOl

new plants and partly by vigorous expansion of the crowns of old ones (fig 11) Although the increase in the grgtwth of sagebrush and other shrubs tended to compensate for the losses of grasses and weeds in the stand the total density of the cover in 1930 was about 15 percent less than in 1924

Further indication of the manner in which such heavy grazing reshyduced the forage value of this range was gnined from t1 comparison for the years 1923-32 of the bast11 aret1 of perennial grasses on a me telshysquare quadrat laid out on a portion of this paddock that was fairly representative of the area as a whole As may be seen from table 11

24 TECHNICAL BULLETIN 600 U S DEPT OF AGltICULTURE

the decrease in basal area for the entire period was 92 percent The weakening effects of this character of grazin~ is illustrated also by the declining vigor of the herbaceous vegetatIOn to the degree that

during the last 4 years of the grazing period

_ PALATABLE VEGETATION the development of thecJ UNPALATABLE VEGETATION herbltceous vegetation to 2-inch height growth lagged from 2 to 14 days behind the time when similar plants on less heavily grazed range reached thi s stage RLlldom measurements of height growth and flower-stalk counts conshyfirmed these evidences Bnlsumroot plants on

1924 1930 this area produced anshy

FIGURE ll-Elfect of heavy continuous sprln~ and late faUuse on the palatability of rango coer hot ween 11)24 and JU30 nually only one or two

flower stalks from 4 to 5 inches in length per plant whereas 12 to 15 flower stalks 12 to 20 inches in length were produced on balsamroot plants nearby under moderate grazing

TAnIE ll-The shrinkage in basal area of perennial grasses on a representative meter quadrat in paddock 2 and the lag in rCUlUne~s for grazing (2-inch height growth) as compared to protected ranye

Lag Innusal lag In I IBasal ILag In DasalYenrs ur~u rcadlmiddot Yenrs urell rcadlmiddot Years urea readlmiddot

I ness

_ ___ I nessness ----I ----middot------11-----middot1---shy

(III ])fIV 1 (m naVamp Cm ]Java 80 ())021J bullbull bull bull 108 2 Hla2~~~~H~ al 14 727 U 10aU _ 1) 7 ----shy321 Il 1111 127 n 1 Shrlllkug 355 bullbullbullbullbullbullbullbull I

Furthermore observations maue within a Tod-square portion of this range which WitS protected from grazing in 1930 and 1931 revealed that the balsamroot and other wenJwned pnlntable pI nn ts failed to show any n ppreciable return in vigoL by the end of the spring growing suason in 1931 in spite of the fact that growing conditions were nearly nOlmal in these years Thus it nppeurs that when sagebrush-bullchgrass range of this chamcter is seriously depIcted it will require several years to restore the normal vigor of the rel11nining desirable fornge plants and undoubtedly mnny more years of protection or a combination of protection and Ycry conservative grnzing before new plants will take the place of those killed

The decline in the productivity of this range area is comparable to the depIcted conditiol1 of extensive areas of spring-fall range lands in southeastern Iunho on which grazing is uncontlmiddotolled One band of sheep follows another on the range in the spring utilizing a large percentage of the forage as rnpidly as it is produced In mnny instanees the same ranges nrc ngnin gmzed very heltvily in the fall Such utilization has no pln(c in good mnge mnnngement

----------

----- -------------

INFLUENCE OF GRAZING ON SPRING-JALL SHEEP RANG1~ 25

DEPLETION FROM HEAVY EARLY SPRING AND LATE FALl GRAZING

Several years of early spring grazing repeated at approximately the same period of plant growth each year and followed by fall grazin~ may also be detrimental to sagebrush-bunchgrass range This IS evident in the results of grazing tests in paddock 3 during the years 1924-32 A summary of these tests ill table 12 shows that 36 percent

FIGURE 12-Trend in estimated total annual forage production under heavy early spring and heavy fall use of the range 1024-32

of the forage was utilized on the average in ~1 4-week period each spring starting after grasses reached 2-inch height growth A somewhat larger percent (46) was removed in the fall npresenting a total annual utilization of 82 percent

TABLE 12-Actual use under heavy early spring and late fall grazing of paddock 3 1924-32

Spring grazing Fall grllzing Yearly total Estimiddot mated totalYear For- Formiddot Formiddot forageU~e of Use of Use ofPeriod of use age Period of use age age producmiddotrango range rungoused used used tion I

Sheepmiddot SheeP Sheepmiddot Sheepmiddotdava dllVa davs dav per Permiddot per Permiddot per Permiddot perClert cent acre Ce1lt acre cent acre

1924bullbullbullbull _bullbull Apr 23-Mny 29_ 19 26 34 Oct 5-Nov 13bullbullbull 2814 50 4740 84 5643 1925bullbullbullbullbullbullbullbull AprlJ-MIlY 10 bull 2744 31 Oct Il-Nov 24 5426 iii 8170 92 8880 1926bull_bullbullbullbull Apr 17-MIlY 10bullbull 2997 54 0lt15-Nov2IL 1715 JI 4712 85 65441927___ bull ___ bull Apr 29-MIlY 31 1470 30 Oct 2O-Nov 29__ 2974 00 4444 00 49381928_________ Apr 26-Mny 19__ 1828 52 Oct 20-Dec L__ 1525 43 3353 95 35291029______ MayO-lvrlly2U 881 3U Nov 12-Nov 27 1032 (17 2813 97 2900loao ________ AprIO-JuneLbull 057 45 Nov 5-Nov HI __ 040 31 Iii 03 76 2100 193L___bull Apr 3U-May 21 1217 34 Nov 2-Nov 25 bullbull 1a80 38 297 72 36071932_______bull May i-June L __ bull 9aO 25 Nov I-Nov 12__ 788 21 1718 46 37a5

Average Apr 25-May 2J_ 1061 ao Oct 25-No 22__ 2133 40 3794 82 bull 46 27

I Estlmated totnl forage production (sheepmiddotdnys per acre) average 1924-25 7262 1931-32 3671 Loss in Cornge value between 11124-25 and 1931-32 49 percent

bull Computed averages Seo footnote 4 p O

26 TECHNICAL BULLETIN 600 U S DEPT OF AGRICULTURE

This area produced un estimated wemge of 73 sheep-days of feed per acre in the first 2 years of the experiment But here as in other paddocks heavily gmzed in the spring enrly forage production declined consistently to a low leyel by the end of the period (fig 12) The average of the 2 years 1931 and 1932 was ouly 37 sheep-days or nearly 50 percent less than the average of the first 2 years Although this was an improvement oyer the preceding 2 years attributable to the more fayorable growing conditions in 1932 it did not tfled materially the definite downward trend for the period as a wbole

As under heayy continuous spring grazing in paddock 2 this conshysiderable decline in ayailable forage resulted in a very sigllificant change in the composition and hence in the palatability of tho vegetashytion as shown in table 13 und figure 13 In 1924 grass and browse

coverednearly eq ual porshy_ PALATABLE tions of the paddock butVEGETATION

i cJ UNPALATABLE VEGETATION by 1930 the density of sect16r -------------------4 shrubs increased more 5 than 50 percent and ~ covered about three and12~----------------__4

one-half times the grass area Most of this inshycrease was due to the expansion of the size of sagebrush and other relatively unpnlntable shrubs rhe reduction in density of the grasses

1930 by more than 50 percent FIGlltE 13-ElTecl of hClIY cllrly spring lind late filII grazing OIl and that of the weeds bv

pnilltubility of range covor between JU24 and 1D30 18 perceni ([e Inrgely

due to the destruction of the most desirable forage plants such as wheatgrass bluegrass clepis and balsarnroot 110reorcr ns is evishydent in table 141 the baslLl UJca of pcrennial gmsses Oil lL metershysquare quadrat decreased between 1926 and 1932 by 77 pereent

In addition to these ~ross changes in the plant cover table 14 revenls a measurable decrease ill the vigor of the herbaceous plants during the last 4 years of the study period Two-inch-height growth was not attained on this area until 6 to 10 days after the same stage of developshyment was reached on more consefTatively grazed adjacent range Moreover flower stalks on the bnlsamroot plants were neither so numerous nor so long-stemmed as those on protected range

TABLE 13-Effect of heatmiddoty early slJring and laic fall grazing on paddork 3 a shown by the relative C01lt1Josilion and ground cover oj the vegealion in 1924 and 1930

I reu of l lndduck COlr(d hy vcgctlltlon

Composition of ________-________ Class of forage cover rolal cOvtr Jlailltubll COVllr

_________ ~~~ 102middot ~ Chunge - lJ2~ I~ Chung

P~TCr71t Percent Perceltt Percent PtrCtmt IJtreeIlt Perct7lt Percent Drowsmiddotbullbullbullbullbullbullbullbull_bullbullbull 4118 MOfgt 11middot15 17fgt +51 I1S Ili2 +51 Oms ________ 1029 1877 1U811 bIIS -fia 7114 184 -[2 Wecds__ ~~ 515 ~~~~~

Tuta lUOOO HX1IKI 2769 2703 -21 1226 bullbull 2 -41

24 TECHNICAL BULLETIN 600 U S DEPT OF AGltICULTURE

the decrease in basal area for the entire period was 92 percent The weakening effects of this character of grazin~ is illustrated also by the declining vigor of the herbaceous vegetatIOn to the degree that

during the last 4 years of the grazing period

_ PALATABLE VEGETATION the development of thecJ UNPALATABLE VEGETATION herbltceous vegetation to 2-inch height growth lagged from 2 to 14 days behind the time when similar plants on less heavily grazed range reached thi s stage RLlldom measurements of height growth and flower-stalk counts conshyfirmed these evidences Bnlsumroot plants on

1924 1930 this area produced anshy

FIGURE ll-Elfect of heavy continuous sprln~ and late faUuse on the palatability of rango coer hot ween 11)24 and JU30 nually only one or two

flower stalks from 4 to 5 inches in length per plant whereas 12 to 15 flower stalks 12 to 20 inches in length were produced on balsamroot plants nearby under moderate grazing

TAnIE ll-The shrinkage in basal area of perennial grasses on a representative meter quadrat in paddock 2 and the lag in rCUlUne~s for grazing (2-inch height growth) as compared to protected ranye

Lag Innusal lag In I IBasal ILag In DasalYenrs ur~u rcadlmiddot Yenrs urell rcadlmiddot Years urea readlmiddot

I ness

_ ___ I nessness ----I ----middot------11-----middot1---shy

(III ])fIV 1 (m naVamp Cm ]Java 80 ())021J bullbull bull bull 108 2 Hla2~~~~H~ al 14 727 U 10aU _ 1) 7 ----shy321 Il 1111 127 n 1 Shrlllkug 355 bullbullbullbullbullbullbullbull I

Furthermore observations maue within a Tod-square portion of this range which WitS protected from grazing in 1930 and 1931 revealed that the balsamroot and other wenJwned pnlntable pI nn ts failed to show any n ppreciable return in vigoL by the end of the spring growing suason in 1931 in spite of the fact that growing conditions were nearly nOlmal in these years Thus it nppeurs that when sagebrush-bullchgrass range of this chamcter is seriously depIcted it will require several years to restore the normal vigor of the rel11nining desirable fornge plants and undoubtedly mnny more years of protection or a combination of protection and Ycry conservative grnzing before new plants will take the place of those killed

The decline in the productivity of this range area is comparable to the depIcted conditiol1 of extensive areas of spring-fall range lands in southeastern Iunho on which grazing is uncontlmiddotolled One band of sheep follows another on the range in the spring utilizing a large percentage of the forage as rnpidly as it is produced In mnny instanees the same ranges nrc ngnin gmzed very heltvily in the fall Such utilization has no pln(c in good mnge mnnngement

----------

----- -------------

INFLUENCE OF GRAZING ON SPRING-JALL SHEEP RANG1~ 25

DEPLETION FROM HEAVY EARLY SPRING AND LATE FALl GRAZING

Several years of early spring grazing repeated at approximately the same period of plant growth each year and followed by fall grazin~ may also be detrimental to sagebrush-bunchgrass range This IS evident in the results of grazing tests in paddock 3 during the years 1924-32 A summary of these tests ill table 12 shows that 36 percent

FIGURE 12-Trend in estimated total annual forage production under heavy early spring and heavy fall use of the range 1024-32

of the forage was utilized on the average in ~1 4-week period each spring starting after grasses reached 2-inch height growth A somewhat larger percent (46) was removed in the fall npresenting a total annual utilization of 82 percent

TABLE 12-Actual use under heavy early spring and late fall grazing of paddock 3 1924-32

Spring grazing Fall grllzing Yearly total Estimiddot mated totalYear For- Formiddot Formiddot forageU~e of Use of Use ofPeriod of use age Period of use age age producmiddotrango range rungoused used used tion I

Sheepmiddot SheeP Sheepmiddot Sheepmiddotdava dllVa davs dav per Permiddot per Permiddot per Permiddot perClert cent acre Ce1lt acre cent acre

1924bullbullbullbull _bullbull Apr 23-Mny 29_ 19 26 34 Oct 5-Nov 13bullbullbull 2814 50 4740 84 5643 1925bullbullbullbullbullbullbullbull AprlJ-MIlY 10 bull 2744 31 Oct Il-Nov 24 5426 iii 8170 92 8880 1926bull_bullbullbullbull Apr 17-MIlY 10bullbull 2997 54 0lt15-Nov2IL 1715 JI 4712 85 65441927___ bull ___ bull Apr 29-MIlY 31 1470 30 Oct 2O-Nov 29__ 2974 00 4444 00 49381928_________ Apr 26-Mny 19__ 1828 52 Oct 20-Dec L__ 1525 43 3353 95 35291029______ MayO-lvrlly2U 881 3U Nov 12-Nov 27 1032 (17 2813 97 2900loao ________ AprIO-JuneLbull 057 45 Nov 5-Nov HI __ 040 31 Iii 03 76 2100 193L___bull Apr 3U-May 21 1217 34 Nov 2-Nov 25 bullbull 1a80 38 297 72 36071932_______bull May i-June L __ bull 9aO 25 Nov I-Nov 12__ 788 21 1718 46 37a5

Average Apr 25-May 2J_ 1061 ao Oct 25-No 22__ 2133 40 3794 82 bull 46 27

I Estlmated totnl forage production (sheepmiddotdnys per acre) average 1924-25 7262 1931-32 3671 Loss in Cornge value between 11124-25 and 1931-32 49 percent

bull Computed averages Seo footnote 4 p O

26 TECHNICAL BULLETIN 600 U S DEPT OF AGRICULTURE

This area produced un estimated wemge of 73 sheep-days of feed per acre in the first 2 years of the experiment But here as in other paddocks heavily gmzed in the spring enrly forage production declined consistently to a low leyel by the end of the period (fig 12) The average of the 2 years 1931 and 1932 was ouly 37 sheep-days or nearly 50 percent less than the average of the first 2 years Although this was an improvement oyer the preceding 2 years attributable to the more fayorable growing conditions in 1932 it did not tfled materially the definite downward trend for the period as a wbole

As under heayy continuous spring grazing in paddock 2 this conshysiderable decline in ayailable forage resulted in a very sigllificant change in the composition and hence in the palatability of tho vegetashytion as shown in table 13 und figure 13 In 1924 grass and browse

coverednearly eq ual porshy_ PALATABLE tions of the paddock butVEGETATION

i cJ UNPALATABLE VEGETATION by 1930 the density of sect16r -------------------4 shrubs increased more 5 than 50 percent and ~ covered about three and12~----------------__4

one-half times the grass area Most of this inshycrease was due to the expansion of the size of sagebrush and other relatively unpnlntable shrubs rhe reduction in density of the grasses

1930 by more than 50 percent FIGlltE 13-ElTecl of hClIY cllrly spring lind late filII grazing OIl and that of the weeds bv

pnilltubility of range covor between JU24 and 1D30 18 perceni ([e Inrgely

due to the destruction of the most desirable forage plants such as wheatgrass bluegrass clepis and balsarnroot 110reorcr ns is evishydent in table 141 the baslLl UJca of pcrennial gmsses Oil lL metershysquare quadrat decreased between 1926 and 1932 by 77 pereent

In addition to these ~ross changes in the plant cover table 14 revenls a measurable decrease ill the vigor of the herbaceous plants during the last 4 years of the study period Two-inch-height growth was not attained on this area until 6 to 10 days after the same stage of developshyment was reached on more consefTatively grazed adjacent range Moreover flower stalks on the bnlsamroot plants were neither so numerous nor so long-stemmed as those on protected range

TABLE 13-Effect of heatmiddoty early slJring and laic fall grazing on paddork 3 a shown by the relative C01lt1Josilion and ground cover oj the vegealion in 1924 and 1930

I reu of l lndduck COlr(d hy vcgctlltlon

Composition of ________-________ Class of forage cover rolal cOvtr Jlailltubll COVllr

_________ ~~~ 102middot ~ Chunge - lJ2~ I~ Chung

P~TCr71t Percent Perceltt Percent PtrCtmt IJtreeIlt Perct7lt Percent Drowsmiddotbullbullbullbullbullbullbullbull_bullbullbull 4118 MOfgt 11middot15 17fgt +51 I1S Ili2 +51 Oms ________ 1029 1877 1U811 bIIS -fia 7114 184 -[2 Wecds__ ~~ 515 ~~~~~

Tuta lUOOO HX1IKI 2769 2703 -21 1226 bullbull 2 -41

----------

----- -------------

INFLUENCE OF GRAZING ON SPRING-JALL SHEEP RANG1~ 25

DEPLETION FROM HEAVY EARLY SPRING AND LATE FALl GRAZING

Several years of early spring grazing repeated at approximately the same period of plant growth each year and followed by fall grazin~ may also be detrimental to sagebrush-bunchgrass range This IS evident in the results of grazing tests in paddock 3 during the years 1924-32 A summary of these tests ill table 12 shows that 36 percent

FIGURE 12-Trend in estimated total annual forage production under heavy early spring and heavy fall use of the range 1024-32

of the forage was utilized on the average in ~1 4-week period each spring starting after grasses reached 2-inch height growth A somewhat larger percent (46) was removed in the fall npresenting a total annual utilization of 82 percent

TABLE 12-Actual use under heavy early spring and late fall grazing of paddock 3 1924-32

Spring grazing Fall grllzing Yearly total Estimiddot mated totalYear For- Formiddot Formiddot forageU~e of Use of Use ofPeriod of use age Period of use age age producmiddotrango range rungoused used used tion I

Sheepmiddot SheeP Sheepmiddot Sheepmiddotdava dllVa davs dav per Permiddot per Permiddot per Permiddot perClert cent acre Ce1lt acre cent acre

1924bullbullbullbull _bullbull Apr 23-Mny 29_ 19 26 34 Oct 5-Nov 13bullbullbull 2814 50 4740 84 5643 1925bullbullbullbullbullbullbullbull AprlJ-MIlY 10 bull 2744 31 Oct Il-Nov 24 5426 iii 8170 92 8880 1926bull_bullbullbullbull Apr 17-MIlY 10bullbull 2997 54 0lt15-Nov2IL 1715 JI 4712 85 65441927___ bull ___ bull Apr 29-MIlY 31 1470 30 Oct 2O-Nov 29__ 2974 00 4444 00 49381928_________ Apr 26-Mny 19__ 1828 52 Oct 20-Dec L__ 1525 43 3353 95 35291029______ MayO-lvrlly2U 881 3U Nov 12-Nov 27 1032 (17 2813 97 2900loao ________ AprIO-JuneLbull 057 45 Nov 5-Nov HI __ 040 31 Iii 03 76 2100 193L___bull Apr 3U-May 21 1217 34 Nov 2-Nov 25 bullbull 1a80 38 297 72 36071932_______bull May i-June L __ bull 9aO 25 Nov I-Nov 12__ 788 21 1718 46 37a5

Average Apr 25-May 2J_ 1061 ao Oct 25-No 22__ 2133 40 3794 82 bull 46 27

I Estlmated totnl forage production (sheepmiddotdnys per acre) average 1924-25 7262 1931-32 3671 Loss in Cornge value between 11124-25 and 1931-32 49 percent

bull Computed averages Seo footnote 4 p O

26 TECHNICAL BULLETIN 600 U S DEPT OF AGRICULTURE

This area produced un estimated wemge of 73 sheep-days of feed per acre in the first 2 years of the experiment But here as in other paddocks heavily gmzed in the spring enrly forage production declined consistently to a low leyel by the end of the period (fig 12) The average of the 2 years 1931 and 1932 was ouly 37 sheep-days or nearly 50 percent less than the average of the first 2 years Although this was an improvement oyer the preceding 2 years attributable to the more fayorable growing conditions in 1932 it did not tfled materially the definite downward trend for the period as a wbole

As under heayy continuous spring grazing in paddock 2 this conshysiderable decline in ayailable forage resulted in a very sigllificant change in the composition and hence in the palatability of tho vegetashytion as shown in table 13 und figure 13 In 1924 grass and browse

coverednearly eq ual porshy_ PALATABLE tions of the paddock butVEGETATION

i cJ UNPALATABLE VEGETATION by 1930 the density of sect16r -------------------4 shrubs increased more 5 than 50 percent and ~ covered about three and12~----------------__4

one-half times the grass area Most of this inshycrease was due to the expansion of the size of sagebrush and other relatively unpnlntable shrubs rhe reduction in density of the grasses

1930 by more than 50 percent FIGlltE 13-ElTecl of hClIY cllrly spring lind late filII grazing OIl and that of the weeds bv

pnilltubility of range covor between JU24 and 1D30 18 perceni ([e Inrgely

due to the destruction of the most desirable forage plants such as wheatgrass bluegrass clepis and balsarnroot 110reorcr ns is evishydent in table 141 the baslLl UJca of pcrennial gmsses Oil lL metershysquare quadrat decreased between 1926 and 1932 by 77 pereent

In addition to these ~ross changes in the plant cover table 14 revenls a measurable decrease ill the vigor of the herbaceous plants during the last 4 years of the study period Two-inch-height growth was not attained on this area until 6 to 10 days after the same stage of developshyment was reached on more consefTatively grazed adjacent range Moreover flower stalks on the bnlsamroot plants were neither so numerous nor so long-stemmed as those on protected range

TABLE 13-Effect of heatmiddoty early slJring and laic fall grazing on paddork 3 a shown by the relative C01lt1Josilion and ground cover oj the vegealion in 1924 and 1930

I reu of l lndduck COlr(d hy vcgctlltlon

Composition of ________-________ Class of forage cover rolal cOvtr Jlailltubll COVllr

_________ ~~~ 102middot ~ Chunge - lJ2~ I~ Chung

P~TCr71t Percent Perceltt Percent PtrCtmt IJtreeIlt Perct7lt Percent Drowsmiddotbullbullbullbullbullbullbullbull_bullbullbull 4118 MOfgt 11middot15 17fgt +51 I1S Ili2 +51 Oms ________ 1029 1877 1U811 bIIS -fia 7114 184 -[2 Wecds__ ~~ 515 ~~~~~

Tuta lUOOO HX1IKI 2769 2703 -21 1226 bullbull 2 -41

26 TECHNICAL BULLETIN 600 U S DEPT OF AGRICULTURE

This area produced un estimated wemge of 73 sheep-days of feed per acre in the first 2 years of the experiment But here as in other paddocks heavily gmzed in the spring enrly forage production declined consistently to a low leyel by the end of the period (fig 12) The average of the 2 years 1931 and 1932 was ouly 37 sheep-days or nearly 50 percent less than the average of the first 2 years Although this was an improvement oyer the preceding 2 years attributable to the more fayorable growing conditions in 1932 it did not tfled materially the definite downward trend for the period as a wbole

As under heayy continuous spring grazing in paddock 2 this conshysiderable decline in ayailable forage resulted in a very sigllificant change in the composition and hence in the palatability of tho vegetashytion as shown in table 13 und figure 13 In 1924 grass and browse

coverednearly eq ual porshy_ PALATABLE tions of the paddock butVEGETATION

i cJ UNPALATABLE VEGETATION by 1930 the density of sect16r -------------------4 shrubs increased more 5 than 50 percent and ~ covered about three and12~----------------__4

one-half times the grass area Most of this inshycrease was due to the expansion of the size of sagebrush and other relatively unpnlntable shrubs rhe reduction in density of the grasses

1930 by more than 50 percent FIGlltE 13-ElTecl of hClIY cllrly spring lind late filII grazing OIl and that of the weeds bv

pnilltubility of range covor between JU24 and 1D30 18 perceni ([e Inrgely

due to the destruction of the most desirable forage plants such as wheatgrass bluegrass clepis and balsarnroot 110reorcr ns is evishydent in table 141 the baslLl UJca of pcrennial gmsses Oil lL metershysquare quadrat decreased between 1926 and 1932 by 77 pereent

In addition to these ~ross changes in the plant cover table 14 revenls a measurable decrease ill the vigor of the herbaceous plants during the last 4 years of the study period Two-inch-height growth was not attained on this area until 6 to 10 days after the same stage of developshyment was reached on more consefTatively grazed adjacent range Moreover flower stalks on the bnlsamroot plants were neither so numerous nor so long-stemmed as those on protected range

TABLE 13-Effect of heatmiddoty early slJring and laic fall grazing on paddork 3 a shown by the relative C01lt1Josilion and ground cover oj the vegealion in 1924 and 1930

I reu of l lndduck COlr(d hy vcgctlltlon

Composition of ________-________ Class of forage cover rolal cOvtr Jlailltubll COVllr

_________ ~~~ 102middot ~ Chunge - lJ2~ I~ Chung

P~TCr71t Percent Perceltt Percent PtrCtmt IJtreeIlt Perct7lt Percent Drowsmiddotbullbullbullbullbullbullbullbull_bullbullbull 4118 MOfgt 11middot15 17fgt +51 I1S Ili2 +51 Oms ________ 1029 1877 1U811 bIIS -fia 7114 184 -[2 Wecds__ ~~ 515 ~~~~~

Tuta lUOOO HX1IKI 2769 2703 -21 1226 bullbull 2 -41

--------

INFL1l~NCE OF GUAZING ON HPRING-JAL l5JlEJltP UANOg 27

TABLE 14--Shrinkagc in ba~al arca of perennial grases on a reprc~enl(tive meter quadraUn paddock 3 and their lag in rcadineas for grazing (2-inch-heighpound growlh) CL3 comparcd to protected range

------~--_r---~------r--_r--_~------~--_---~------~------

B I Lagln B 1 LBgin I B IL3tll ll II I LBginYear LltIl nudl Yellr ~relldi Year IS11 rendl YIr nsn reBdl

aren ticss area ness - area ness H orCa ness

-----1-(-- -1----- (II -- Cll~ J)tlVS 1---- em J)aus 1923 474 0 1027 465 0 1030 271 4 IOlL_ 130 8 1926bullbullbull - GOl 0 II~~) IUI 6 l 1~11 bullbull 245 10 I

I I fhrinkRge 315 1 I ji 1

The produ0tivity of this area wus not impaired to the sumo de~rco IlS thnt of paddoek 2 on which 68 pereent of tho forage WIiS removed in the spring but it is clear tlmt the removal of eyen 36 p~rcent of the fornge in the enrly spring when this is repentod nmiddott appioxirnfLtely the same growth period eneh yenr and is followed by the utilizatiOIl of 46 porcent of the remaining feed in the fall or n totnl of 82 percent will result in such serious damage to the range as to preclude considerashytion of this form of use as a practienl system of management on sageshybrush-buuchgrlt~ss lands

DEPLETION FROM HEAVY LATE SPIUNG AND LATE FALL GltAZING

Persistent henvy spring use of these Tanges even when deferred uutil 6-inch-height growth of gmsses is attained and continued for llll average of only 23 days mlLy lesult in vely unsntisfactory cOldi tion s if the rnnge is henvily used in the fall This is evident in tnble 15 showing the results obtnined on paddock 8 On the nvemge 53 pershycent of the fornge was consumed in the spring uJter the prinripnl grasses renched a 6-inch-height growth lPall use made up au lwemge total annunl utilizntion of 90 percent of the forage

Feed produced on this nrea 11Veraged 66 sheep-days for 1he first 2 yenrs of the 9-yenr period of study This is less than 011 paddock 3 and the better pnddocks (7 und 1) the difTetenee being due to lower density of paIIltable vegeta1ion on this paddoek-particularly to the unusually small percenta~e of weed feod In other respeets however this paddock was fairly characteristic of the stutioll rangC

TABLE 15--Actual use under heavy laic spring and laic fall gra~ing of 11Oddock 8 1[)2i-S2

S(lrin~ gnl7ing Fail grazing IYeBrly (olBI Estmiddot 1I1llhd

totnlYear Formiddot Formiddot Formiddot forngtlsr or ls( Qr FscofPeriod or uso tut lcrioci or use Igo n~e producmiddotTfUlge raug~ rongeUl~d used used tion

ShuT ShaP--~

Sheepmiddot ShupshydlV Pamiddot rlay Pcrmiddot rtlV PITmiddot clIU

prr llCTt emt 1gter (Jere cent 1tmiddotr IIcrr c(lIt 1Jer acre 1924bullbullbullbullbullbullbullbull May 2-Mny ~IL_ 1847 as Oct [Nov 11 2820 fin 46 tl7 97 4811 1025 __ bullbull Mny 5-Junc 10 ft 27 05 Oct IfNov 19 2459 ao 7S86 95 81()1 102(1bullbullbullbullbullbullbull May i-MBy 26 40 fl5 74 Oct lrOtt 28 l(Jfgt(l 26 41 21 IOU 4121 1927 MlyZl-Junc 15 1440 (( Nomiddot 14-N(lv~Ilbull li~ J2 ~U 4052 95 5211 1928 1111Y 8-MlY bullbull 2229 62 Oct 2(l-Nlw 24 11 on a3 H25 us 1605 1929_ MIIY 19-JlInc 12 18M il Oct31-Nov 11 _ II no 2middot 2410 95 21 a7 11I1() May 14-)IIIY 28 n1l1 fiO Nov u-Nov JO 8 II 4() 1802 gO 2(1(12 1931 __ MllY II-Julle 2 bull 705 11 Nov 2-N(I 25 101ll (~I 2401 07 24~ i7 luIL_ -_--------- - tJ () Nov J-Nt)t ~I 17011 [tt 17 tKl flO I-IIMI

~c_Mfitl~lpoundS~ 2] 74 ~ OcL 27-)ltov 17 ~ 3 17 aiOi 00 3iiiii

~ ~ ~

I Estimated total forl~e production (Shcllpmiddotdays (lcr aen) IIv(mgl 1IJ2middot1-25 (155(1 W31-2 ~~)ao Loss in orogo value between lU24-25 and 1931-32 fi5 percent

gycar avemgo 3 Com (luted IIVCfllRC$ Se footuole 4 p G

28 TECHNICAL BULLETIN 600) U S DEPT OF AGRICULTURE

During the first 5 years of tbe study forage production varied from year to year in response to genernl growing conditions (fig 14) The estimated feed in sheep-days wns high in 1925 when moisture was above average and in 1927 when it was average and low during the dry years of 1924 1926 and 1928 Following the poor year of 1928

~ ~ t ~tiOl----

~ ~ I

(j

~

FIGtIIE 14-1rcnd in totai nnnllnl fornge production under hellvy lnte spring nnd lllte fall use of range 1924-32

however the berbaceolls vegetfltion fuiled to respond to the rather fn Yornble conditions in ] 929 (Ine by 1930 the n umber of sheep-days of feed dropped to the low hYel of 20 The upward trend ill forage prod uction during ] 931 flnd 1932 only feebly compensated for the sharp decline of the 2 preceding YCflfS Feed produced in the last 2

years of the experimenshytal period averaged 55

_ PALATABLE VEGETATION percent less than that ~ cJ UNPALATABLE VEGETATION produced in the first 2~16~-------------------4--~--------~

yClUS~ AI thougb the delayed~ use of this area in the spring appeared to maintain the grazing value of the her b ashyecous vegetation for a period of 4 years as compnred to a period of only 2 years on

1930 paddock 2 which was1924 grazed earlier and for

FIGURE 15-ElTect of henvy lnte sprmg aud lnte fnll hrnzing on tbe 1 dmiddot th palatauility of range COlr bcLW~lll lU2middot uud lJao a onger peno ill e

spring the removal of more than hnlf of the nvaihtble fornge in the spring and up to a total of 90 percent of the forage in the fILII together with the effect of grazing at n fixed period each spring Jesulted in serious damage to the range cover Although by 1930 the shrubs on this range increased 27 pershycent in density (table 16) there was no increase in their palatability

INFLUENCg 01lt GUAZlNG ON HPHING-]ALL ~HEEP HANGI 29

Meanwhile palatable grasses decreased 65 percent and palatable weeds 64 percent (fig 15) On a meter-square quadrat within the area the decline in bllsnl area of the grasses wns also pronounced amounting to a net loss of 86 percent The progress of this decline is shown in table 17

TABLE lu-Effect of heavy laic spring and late fall grazing on paddock 8 as shown by the relatitmiddote composition and ground cover of the vegetalion in 1924 and 1930

I Areu ot plIltldo~k rOCrcd by egetutioll

Composition ot(over (h~s ot tortlge fotal rover Pulntnblu cOer

lr24 i 1030 -T~~--~=~ -l~- j 1930 Chunge

-+-~--~-- --1----- -- ---r --I--------shy Parrnl Ptrcell PrrClt1l1 I Perce lit Ptrctnl i Pacrnt Percent I Perce lit

Browse middot1 00 75 00 I 12 RmiddotI j 1630 i +2 j 1 10 i I ~O 0 GnlSS _ 4S311 ~OS la81 4(2 -fl 991 I 34i -65 Weeds Gil -1221 1110 92 -521 U9 36 -fgti

1otaL__ bullbull____ bullbullbull woOo1oo00- 2S S-I---T----1210(503i----SS _________L_~I_gto_ j I TABLE 17-The shrinkage in basal area of l)erenniul grasses 01 a representative

meier quadrat in paddtJck 8 and (eir lay in readiness for grazing (6-inch-height growth) as compared to prol~cted range

I I Lag i Lag II t Lng ill I Lag v 0 Bnsnl in YelJs Basal in II Years nQSU11 ill I enrs Basal ill ers area Irendi- i uren 1 reudlmiddot j urea rendi L aren rendishyI Iness I I ness II ness ness ___ I

-~~-I em i-- 21-D-a-v $- --l-e-m- _C_III_ -_J)a_V_- (-C-III- D-av- 1923 ____ 610 0 1928_______ bullbullbull a 1930 r 155 S 1932____ b5 I 4 1926 67 i 0 1U20 __ I 1 1931 r ~O31 3 --- shy1927 290 0 j i Shrinlmge b31 __ bullbull _ ___ _ _ ~_~~__~ c___bull__~_c_ ______

Other obsen-able effects of this system of grazing showed that the vigorous expansion of sagebrush and other relnthely unpalatable plants was accompanied by n sharp decline in the yigor of the surshyltjving palntable grasses and weeds In 1928 the grasses did not rench u-inch-height growth until 3 dnys later than on more onsernltiYely grazed and protected mnge and in 1929 and 1930 tlus stnge of dcshyyclopment WllS dclayed 1 nnd 8 days lcspediYely During these 3 years weed-flower production Wits llotic(nbly l(ss thnn on the station 1llnge llS tl whole In] 931 nnel1932 nlthough general growing coushy(litions were somewhnt more fn vOlnble tllnn ill 1929 and 1030 there was still a Ing of 3 to 4 dl1TS in u-ineh-lwight glOwth of grasses anel weed-flower prod uction continued to be negligible

Although there was no llppnrcnt ehange in the grazing value of the vegetation on tllis urel1 during tbe Ilrst 4 yonIS of Stll(~YI otlwr than ehung(s nonnnlly to be exp((ted fIom weuthN fluctUlltlOIlS the extent to wluch the palatable f01lge was reduced in density or othershywise replaced by less pn latable shuhs dUIing the ltlSt 5 yenrs of the study clenJly indicates that serious depktioll occutlecl and that this system of grazing nnd intcnsity of use hns no prtlcticnl vlllue in rangr-sheep productioll

28 TECHNICAL BULLETIN 600) U S DEPT OF AGRICULTURE

During the first 5 years of tbe study forage production varied from year to year in response to genernl growing conditions (fig 14) The estimated feed in sheep-days wns high in 1925 when moisture was above average and in 1927 when it was average and low during the dry years of 1924 1926 and 1928 Following the poor year of 1928

~ ~ t ~tiOl----

~ ~ I

(j

~

FIGtIIE 14-1rcnd in totai nnnllnl fornge production under hellvy lnte spring nnd lllte fall use of range 1924-32

however the berbaceolls vegetfltion fuiled to respond to the rather fn Yornble conditions in ] 929 (Ine by 1930 the n umber of sheep-days of feed dropped to the low hYel of 20 The upward trend ill forage prod uction during ] 931 flnd 1932 only feebly compensated for the sharp decline of the 2 preceding YCflfS Feed produced in the last 2

years of the experimenshytal period averaged 55

_ PALATABLE VEGETATION percent less than that ~ cJ UNPALATABLE VEGETATION produced in the first 2~16~-------------------4--~--------~

yClUS~ AI thougb the delayed~ use of this area in the spring appeared to maintain the grazing value of the her b ashyecous vegetation for a period of 4 years as compnred to a period of only 2 years on

1930 paddock 2 which was1924 grazed earlier and for

FIGURE 15-ElTect of henvy lnte sprmg aud lnte fnll hrnzing on tbe 1 dmiddot th palatauility of range COlr bcLW~lll lU2middot uud lJao a onger peno ill e

spring the removal of more than hnlf of the nvaihtble fornge in the spring and up to a total of 90 percent of the forage in the fILII together with the effect of grazing at n fixed period each spring Jesulted in serious damage to the range cover Although by 1930 the shrubs on this range increased 27 pershycent in density (table 16) there was no increase in their palatability

INFLUENCg 01lt GUAZlNG ON HPHING-]ALL ~HEEP HANGI 29

Meanwhile palatable grasses decreased 65 percent and palatable weeds 64 percent (fig 15) On a meter-square quadrat within the area the decline in bllsnl area of the grasses wns also pronounced amounting to a net loss of 86 percent The progress of this decline is shown in table 17

TABLE lu-Effect of heavy laic spring and late fall grazing on paddock 8 as shown by the relatitmiddote composition and ground cover of the vegetalion in 1924 and 1930

I Areu ot plIltldo~k rOCrcd by egetutioll

Composition ot(over (h~s ot tortlge fotal rover Pulntnblu cOer

lr24 i 1030 -T~~--~=~ -l~- j 1930 Chunge

-+-~--~-- --1----- -- ---r --I--------shy Parrnl Ptrcell PrrClt1l1 I Perce lit Ptrctnl i Pacrnt Percent I Perce lit

Browse middot1 00 75 00 I 12 RmiddotI j 1630 i +2 j 1 10 i I ~O 0 GnlSS _ 4S311 ~OS la81 4(2 -fl 991 I 34i -65 Weeds Gil -1221 1110 92 -521 U9 36 -fgti

1otaL__ bullbull____ bullbullbull woOo1oo00- 2S S-I---T----1210(503i----SS _________L_~I_gto_ j I TABLE 17-The shrinkage in basal area of l)erenniul grasses 01 a representative

meier quadrat in paddtJck 8 and (eir lay in readiness for grazing (6-inch-height growth) as compared to prol~cted range

I I Lag i Lag II t Lng ill I Lag v 0 Bnsnl in YelJs Basal in II Years nQSU11 ill I enrs Basal ill ers area Irendi- i uren 1 reudlmiddot j urea rendi L aren rendishyI Iness I I ness II ness ness ___ I

-~~-I em i-- 21-D-a-v $- --l-e-m- _C_III_ -_J)a_V_- (-C-III- D-av- 1923 ____ 610 0 1928_______ bullbullbull a 1930 r 155 S 1932____ b5 I 4 1926 67 i 0 1U20 __ I 1 1931 r ~O31 3 --- shy1927 290 0 j i Shrinlmge b31 __ bullbull _ ___ _ _ ~_~~__~ c___bull__~_c_ ______

Other obsen-able effects of this system of grazing showed that the vigorous expansion of sagebrush and other relnthely unpalatable plants was accompanied by n sharp decline in the yigor of the surshyltjving palntable grasses and weeds In 1928 the grasses did not rench u-inch-height growth until 3 dnys later than on more onsernltiYely grazed and protected mnge and in 1929 and 1930 tlus stnge of dcshyyclopment WllS dclayed 1 nnd 8 days lcspediYely During these 3 years weed-flower production Wits llotic(nbly l(ss thnn on the station 1llnge llS tl whole In] 931 nnel1932 nlthough general growing coushy(litions were somewhnt more fn vOlnble tllnn ill 1929 and 1030 there was still a Ing of 3 to 4 dl1TS in u-ineh-lwight glOwth of grasses anel weed-flower prod uction continued to be negligible

Although there was no llppnrcnt ehange in the grazing value of the vegetation on tllis urel1 during tbe Ilrst 4 yonIS of Stll(~YI otlwr than ehung(s nonnnlly to be exp((ted fIom weuthN fluctUlltlOIlS the extent to wluch the palatable f01lge was reduced in density or othershywise replaced by less pn latable shuhs dUIing the ltlSt 5 yenrs of the study clenJly indicates that serious depktioll occutlecl and that this system of grazing nnd intcnsity of use hns no prtlcticnl vlllue in rangr-sheep productioll

INFLUENCg 01lt GUAZlNG ON HPHING-]ALL ~HEEP HANGI 29

Meanwhile palatable grasses decreased 65 percent and palatable weeds 64 percent (fig 15) On a meter-square quadrat within the area the decline in bllsnl area of the grasses wns also pronounced amounting to a net loss of 86 percent The progress of this decline is shown in table 17

TABLE lu-Effect of heavy laic spring and late fall grazing on paddock 8 as shown by the relatitmiddote composition and ground cover of the vegetalion in 1924 and 1930

I Areu ot plIltldo~k rOCrcd by egetutioll

Composition ot(over (h~s ot tortlge fotal rover Pulntnblu cOer

lr24 i 1030 -T~~--~=~ -l~- j 1930 Chunge

-+-~--~-- --1----- -- ---r --I--------shy Parrnl Ptrcell PrrClt1l1 I Perce lit Ptrctnl i Pacrnt Percent I Perce lit

Browse middot1 00 75 00 I 12 RmiddotI j 1630 i +2 j 1 10 i I ~O 0 GnlSS _ 4S311 ~OS la81 4(2 -fl 991 I 34i -65 Weeds Gil -1221 1110 92 -521 U9 36 -fgti

1otaL__ bullbull____ bullbullbull woOo1oo00- 2S S-I---T----1210(503i----SS _________L_~I_gto_ j I TABLE 17-The shrinkage in basal area of l)erenniul grasses 01 a representative

meier quadrat in paddtJck 8 and (eir lay in readiness for grazing (6-inch-height growth) as compared to prol~cted range

I I Lag i Lag II t Lng ill I Lag v 0 Bnsnl in YelJs Basal in II Years nQSU11 ill I enrs Basal ill ers area Irendi- i uren 1 reudlmiddot j urea rendi L aren rendishyI Iness I I ness II ness ness ___ I

-~~-I em i-- 21-D-a-v $- --l-e-m- _C_III_ -_J)a_V_- (-C-III- D-av- 1923 ____ 610 0 1928_______ bullbullbull a 1930 r 155 S 1932____ b5 I 4 1926 67 i 0 1U20 __ I 1 1931 r ~O31 3 --- shy1927 290 0 j i Shrinlmge b31 __ bullbull _ ___ _ _ ~_~~__~ c___bull__~_c_ ______

Other obsen-able effects of this system of grazing showed that the vigorous expansion of sagebrush and other relnthely unpalatable plants was accompanied by n sharp decline in the yigor of the surshyltjving palntable grasses and weeds In 1928 the grasses did not rench u-inch-height growth until 3 dnys later than on more onsernltiYely grazed and protected mnge and in 1929 and 1930 tlus stnge of dcshyyclopment WllS dclayed 1 nnd 8 days lcspediYely During these 3 years weed-flower production Wits llotic(nbly l(ss thnn on the station 1llnge llS tl whole In] 931 nnel1932 nlthough general growing coushy(litions were somewhnt more fn vOlnble tllnn ill 1929 and 1030 there was still a Ing of 3 to 4 dl1TS in u-ineh-lwight glOwth of grasses anel weed-flower prod uction continued to be negligible

Although there was no llppnrcnt ehange in the grazing value of the vegetation on tllis urel1 during tbe Ilrst 4 yonIS of Stll(~YI otlwr than ehung(s nonnnlly to be exp((ted fIom weuthN fluctUlltlOIlS the extent to wluch the palatable f01lge was reduced in density or othershywise replaced by less pn latable shuhs dUIing the ltlSt 5 yenrs of the study clenJly indicates that serious depktioll occutlecl and that this system of grazing nnd intcnsity of use hns no prtlcticnl vlllue in rangr-sheep productioll

30 TECHNICAL BULLETIN GOO U fi DEPT OP AGlUOGLTUng

DEPLETION ntOM MODERATE LATE SPRING AND HEAVY ALL GRAZING

or the fOllr pnsLuPS in which gmzing yalues decreased the least change occurred in pndcloek 7 where approxinately 19 percent of the forage WitS utilized in an lwemge period of 20 elays in the spring after the Ij(~rbltceous vpgttatioll renehed 6-ineh height growth and heaT fall glnzing brought the totuluse up to 85 percent As may be Heen from the ltcord of depletion SUllUllar1zecl in ttLble 8 an average of 82 sheep-dllJs of feed pet nere wns prociueed on this aTelL in 1924 ancl1925 or from 9 to ] 0 dnys more than OIl filly of the other paddocks thus fnl onsitiflld This is clue to the Jflatin-Iy grelltll plrcentnge of pnlatnble foragt in tho wgetatie cover but in other respects the muge was simillu including species present and climate and soil factors

TABLE lB-Actuol 11M lIndr 1Iorierall lale sprng (11d JJl(IY fall grazing oj l)(1ddock 7 J)J4~S2

1 BsUlIltllell totnl Iorn~j1 protilwtion (shelp-duys tlPrUtmiddotnlIIIprn~ll HIfmiddot [II hLsrj WU t f)I)fM lu~~ ill furnJI vuhw hltWtllU HImiddotI~fJ Hud IHU tU Jl(I(~(lnl

J CmufJutcd tlmiddotertiJW~ Sc( (JOtiwtt fl G

During the 9-1111 lwriod there WtL no dlfini tt downwHrd tnlul in ~ltlzi ng fll lit 1Jw lIuJl1)lr (If RhNp-dnVB oj fp(d IltHfull Ipd from yrill to yelLr Jutlt(r (o~IIy in u(orlillrHl with growing cOIHlitiollS 011 tlll lIlllge ]lLr~e ltillnntities of jplCL huing beC1l protiu(ed in the It 01

generally fumiddotorfl ble Y(flrS or 1925 1927 1929 and 1032 us eompllred to fl lrSS(I yolulne in the dr 01 oth(Iwise unfw()mble ~eHrs of Hl24 1920 ] 92fi H)30 lind ] 931 (fig 10) MoreoI tIWIl WI1S llO obspryshyIlblc dtclil( in the vigor of tho ]ln~( plants HIHl the time ~Ioth stnltecL and the wigh to of glIlSS nnel ((d gIowllt WNC compllrablc with these developl11ents Oil (oIlReldiply glH7td anll ungmzpc rungto As compnrN to 1he HYClage of 1110 fin 2 VttUS of tlH~ lXptIllllental wriod howlI the JllIll bpI of sheep-dtlYS feNI prod lHttL in the last 2 years wus 20 pl1(enl less

ConCurrently with tlws( fltletunLions tlnd tho finnl net loss ill grazshying valut signifiennt (hlIlWs O((uIltd ill tire VtgetfLtingt eonI of this runge ns fHlI1unUlized ill Inble HL 1m (xnmple tire ltlntiwly UIlshy

]JIltttuble shrubs jn(I(HS(d 50 IWJCllti in tPJlgtity from 1924 to 1930 while the dtnity of w((ds Ind grilssN~ dcclcascd 8 nnd ] 5 percent rcspe(ti vply

INCLUJNCg 0]lt GUAIIING ox SPlUNG-FALT RHEEl HANG 31

TABLE 19-Effect oj moderatc lae 8711ng (md h(allI Jail g1(lzing on l)addock 7 as shown by the relatilc COlnlJobulli-ion and ground cover oj the lcgclat-ion in 1924 and 1930

--f -- Arca o[ paddock c~~(-~ glmiddottatinu (orn~~~~~on or I~_____ -

Cluss o[ [rugl- j_______ ~~tnl~Olr ~ Plllltnhll CO~tr

I J021 JUlO J921 11Im (hUIgl IU~I 10ao Chullgu

i- middot-------~I--middot I j)ercrflt I JITCef Perceul pereetlj jJtTCtfJi II jtrcefll PtrCCfll PerCt7It

I3rowsc _~ 3112 52S 1I00 1050 +10 146 202 +18 UrnampL ~_ 13middot10 12112 J21middot1 1028 -ITo IiUU bull 75 -14 WeedS 1728 1421 4Hl 413 -8 J81 200 +10

Tutal lCKJlKImiddotr~~middot ~ I 2~7 lI~~J +12 ~~~~_11~~ _~

PWVHpound Hi Irend In total annual furutt produ(( ion under mOdHrale spring und he~y ftll1 use or ruUll IttN~3~

TAIIIg 20-8hriIlJayI1 ill IillNul ((11 of lcIflIlpoundul Iru~c~ Oil a frJlr(~IIIlIi1 1IJ(lz((1 IIIel( qll(lllmt ill )(udock 7 IIIIIP(ft tdlll thill III 1I111Jazed qlat(~ iltJ(ut(ci ott (middotollprlltlbll lUJJe

lt____ hmiddot___

Ilt~lIll1nJ I hlsaJ HflU

i Ilu- YlIr lur 1 lOllshy

I1rll7(11 grn1tmiddotcl IGrn1luif(rtl1Id 1 nnzed ~rHZtltl qUlIIlrul qUIU-

rats I lItulrntI (jllndmiddot J qUldruLI Ijundshy

rats I I rulS --i -----f Cm

Cm (1ll 1 (1m2 I (Ill) (Om 1~2L Iti7 tilS II~I 2~X I -ISI I 2011~2 lU2(l rl~ 1100 WlIJ -lUI 170 1U27 40 7JU 1111 aun 51n + r Hit l~O

Ullq uestionubly both dIouglt L nlld grllzing eontribu Itd to tlte depletion of this IlIpn ApPllrently elillliltc WilS llluehhss lllflupntiul in this (onnN~tion Own gruzing how(lvel silJec 01( bll~d alcn of gmssts on foul Ilwt(1 qlllldrnts Oil proL(eted llnge us showil in tnble 20 declPttsCd only ] 9 1)(1((11 t bCtwellJ the yCn 18 1923 nnd 1932 bu t on II qundrnt within til( grllzld runglt tllp lCdu(tion WfiS 42 percent

rhese data show also that the decline in the number of estimated sheep-days of feed 011 this area was not nearly so great as on comparshyItble areas on which a thi1(J or more of the forage WHS removed in the sprin~ followed in euell cllse by heavy utilizLtioll of the remaining Ieed 111 the fall Moreoyel sill(~l the decline in the productivity of paddoeks 2 3 8 and 7 wns in eu(ll cuse l1pploxill1l1tely in direct J)roshyportion to the intensity with bieh each WitS utilized in the spring these studies suggest thut the extent to whieh sngebrush-iJunehglnss Iilllge will b(gt c(lpietld hinges hllgely upon the in teIJSity 01 spring use rllis is in nglCelllCnt with studiEs eonducted by Snmpson Ilnd lv(nlmshystell (9) WllO obSCI(lc on the 1rnsntch PlntCHu of Ptnll L reduction ill the yigoJ of llluge pinn ts that were elOPPNl fleq lWlltly in the spriJJg These wOlkprs leeoll1ll1emhd the uspound of n defelI(d nncl rotution system of gJiZil1g ItS d(s(Iilxd by Tnrdille nlld Anderson (8) which voule permit the fOlnge pinIl tR on 1I t kust purt of the lIUge to lNldl maturity befol( Iwing glflz(d und to ])(rJllit regrowth of plnnts thnt (e glH~(d

1924 1925 1926 1927 1928 1929 1930 1931 1932

(ady in til(l SCllSOL ~feftSlllellwnts of ctubohydrnte lIHtnbolisll1 of glllSSts nlllde ]u tel by SlllUPSOl (mel 1lrCrut)r (8) find by M((nrty (6) o(li ltolleiusi Yltly lltn t (xCtssi V(lc (lopping-])Hltieuin lly d tiling til(gt ]wrlod of mnxilllum IIpriul growth--by intederillg with the stiorngt of food s(liutlsJy implll1s the yigor of illlgH plants Thus wl1il( sOllie sprillg gHzing is not inillliltd to the roq uilemellts of rnnge grllsss it is cltur tbut (ollsist(lIlUy ex(essin spring grllzing oYer It pPJlod oj y(lurs lItlst 1)(IlYoided

1tNGl~ IJlIJtOI~JHNI middot(tOllf rA(f oAII (atAZING ONIY

Further (videll(( 10 BubsLullLint0 the uIIlCmbilit of tile sILgll)JuslishywllelL(gmss range to spring gmzing is l(lu(d hY obsllvlltiolHl on the hoek ]HLddo(k 1 hleh n8 gmzed 1Hwil in thH Inll and subjeetcd to the slime clilllll tic il(llW1Nll [lS the other paddocks during the 9-ycal p(riod hut was Jlot utiiized ill the spIillg (fig ]7) On this [wen the 11tngr (stinwtNI SIH(lp-dnrll of f((ld prodlwP( hl 1931 nnd ] 932 despite g(IIIdly lilnv()mhlP dimnUlt onditionsfor til( period

rhese data show also that the decline in the number of estimated sheep-days of feed 011 this area was not nearly so great as on comparshyItble areas on which a thi1(J or more of the forage WHS removed in the sprin~ followed in euell cllse by heavy utilizLtioll of the remaining Ieed 111 the fall Moreoyel sill(~l the decline in the productivity of paddoeks 2 3 8 and 7 wns in eu(ll cuse l1pploxill1l1tely in direct J)roshyportion to the intensity with bieh each WitS utilized in the spring these studies suggest thut the extent to whieh sngebrush-iJunehglnss Iilllge will b(gt c(lpietld hinges hllgely upon the in teIJSity 01 spring use rllis is in nglCelllCnt with studiEs eonducted by Snmpson Ilnd lv(nlmshystell (9) WllO obSCI(lc on the 1rnsntch PlntCHu of Ptnll L reduction ill the yigoJ of llluge pinn ts that were elOPPNl fleq lWlltly in the spriJJg These wOlkprs leeoll1ll1emhd the uspound of n defelI(d nncl rotution system of gJiZil1g ItS d(s(Iilxd by Tnrdille nlld Anderson (8) which voule permit the fOlnge pinIl tR on 1I t kust purt of the lIUge to lNldl maturity befol( Iwing glflz(d und to ])(rJllit regrowth of plnnts thnt (e glH~(d

1924 1925 1926 1927 1928 1929 1930 1931 1932

(ady in til(l SCllSOL ~feftSlllellwnts of ctubohydrnte lIHtnbolisll1 of glllSSts nlllde ]u tel by SlllUPSOl (mel 1lrCrut)r (8) find by M((nrty (6) o(li ltolleiusi Yltly lltn t (xCtssi V(lc (lopping-])Hltieuin lly d tiling til(gt ]wrlod of mnxilllum IIpriul growth--by intederillg with the stiorngt of food s(liutlsJy implll1s the yigor of illlgH plants Thus wl1il( sOllie sprillg gHzing is not inillliltd to the roq uilemellts of rnnge grllsss it is cltur tbut (ollsist(lIlUy ex(essin spring grllzing oYer It pPJlod oj y(lurs lItlst 1)(IlYoided

1tNGl~ IJlIJtOI~JHNI middot(tOllf rA(f oAII (atAZING ONIY

Further (videll(( 10 BubsLullLint0 the uIIlCmbilit of tile sILgll)JuslishywllelL(gmss range to spring gmzing is l(lu(d hY obsllvlltiolHl on the hoek ]HLddo(k 1 hleh n8 gmzed 1Hwil in thH Inll and subjeetcd to the slime clilllll tic il(llW1Nll [lS the other paddocks during the 9-ycal p(riod hut was Jlot utiiized ill the spIillg (fig ]7) On this [wen the 11tngr (stinwtNI SIH(lp-dnrll of f((ld prodlwP( hl 1931 nnd ] 932 despite g(IIIdly lilnv()mhlP dimnUlt onditionsfor til( period

8$ n whole WitS 15 per(eJ] t grentltl than the IWltraglt prod lIcrel ill 1924 and 1925 M01CO(11 hetW(lCll 1924 and H)~() tltrte wus iL subshystantial in(lcnse ill the density of pala table glHsS(1S and weeds while shrubs chiefly St~gpblllSh deelrnspd in dpllsit)r (fig J1-n Sincc InH grazing 1ll1d no seriolls efct upon this 11l1lg( it mllst be (oJl(ludeuthat spring is the (dti(ILl grazing season on areas r---_=--------------- d1alt(terizcd hy sngrshyhrusb-bmwhgmss vegCshytt1tion

Improvement of deshypleted sngebruslJ-hundlshygmss hnds (lUI thus 1(1 obtnuled without sncrishyfieilW (UITellt fOIfw( PlQ(hl(tiotl by deferli~g thc use of the lnI)g(~ until fnlL Tlw YCil-hy- 1924 1930

middot~-n flr plo_Orss of Sll(t FlIlt I lwpmlUlent ill pulalnhillty o( rnl1~e CQIer thrllU~h - climiuoing sprinl UN of orllll

improvement 1S sho-I) in table 21 An nYCmgc oj S3 PCI(pnL of nll nntilnbllt forngc ~WIlS rrInongtd hy grnzing etrh fnll 1whn(D tIle npprosimate nTCtUgc dnte~ of S(ptemh(lmiddot 5 nnd Xovemhtl 30 In the first () years flOl1 93 to 100 per(ent of iilr fornge wns (onsum(d but during the Inst ~ years the pnrl) O((UJfIHC of SIIOW and n (hnnge in breeding OpelHtlOJls nee(sshysitntrd thC Je1lontl of the f1IJimllls before mudl more thnn hnlf of th( nYfl~ilfl hk fornge wns ronsllIl1ed

TABMJ 2J-Aciuol US under hrarv fall grazing (1Iiy of paddock 1 1llr 82

Full gm1in) 1~ti- Fall gTll1ill~ Estishy

Period or Ull

_~ 1l)11ttdI lutni

(1or- (rll~r t ~~ () Ot prmhwr~lnv( llS(l(l t jou

1

Yenr IJlllt~fl llllnl

(f)rn~~ prOdtHshy

lion

-i~- i--- 8h flllV1Uri Pershy

ont ftnt dap JUT

Pcrl ~UllM S2

on Iii

jO) ~U

50 OU j _~ _~nt sn h-t 1 sa 272 H)

-2-_~ ---- _ _ I Estirnllted talnl (()ru~e produrtloIl (ShCfll-dnys per o(rp) III rra~ ll21middot~5 kU2 JUlj ~2 9319 Guin

in (orugc nllm h~t Wl11 192middotHi I l J9I-l2 15 percentComputed nvcrngn itO fnot~~l)t( middot1 p f)

As It l(suJt of this syi(1Il of U~C tll(I W(IC llilLlIV ll1di(atiollS tlw t1 tbe area inereascd ill gmzillg duC First is the il((NIM in fe(d from an average of 81 sheep-dny ill 1924 and IH25 to H3 ill thl lust 2 years Second inventollPs tnk(11 jn ] 024 nnd 1 D30 us sllIlunurized in til hlg 22 revealed thitt the Shlubs had declined fi percent in the stnnd and that glass(s and weeds l(spe(tiv(ly had PHd) ilHJ(ised Ii) and J6 perecnt These (banges included ilJ(ICltsps in the dClIsitY of sud pIlIshyatnble grasses It the blueblllwh Wh(tLtgrHss bluegntsR I1nd lleedlcshygrass (pI 3 B) and of sudl vnluable we(ds tS cl(pis hfdsamroot and Indian-tobacco

34 TECH~nCAL lWLL8TlX 600 U ~ DEPT 01~ AGHWlLJTlm

TAlllE 22-Bffcrt oJ 110 spri110 ornzino (wd hC01Y JaU 11se only on 7JIJddoll J 1 o~ sbouon by lhe relalilC COIll]ioyiUon and ground cOlcr oJ the Icoealian in 1924 arId 1980

(omposlll(111 of ruver

CInss of tornge Jolt1 ro~r

-~-

j ln24 Juao JUllJW J[l21

Jlrowsr Orraquoslt WlUUS

PrrcNli llfff7ll j)errl7Jl Jr) Ii) Iii ~)5 1201 IS 17 middotJO 7U I lJ 4~ 21 )7 J 06 i fj A

Parrlll 1((111 PerrOl1 1141 -i JO J109 middot1 7I1S 7 nu JI) 1 JS j

Pcr((Tlt 11 )rrrnil J09middot -19 11$[ l +21 3UI +21

Total JlO no WJ IJ() () txJ j~ J(J

Exerpt for unJ)]lIlJ YJlriJJii()lls O((usj()JlPd hY I1IHtunl ions j n WPl1 t IWI thrle wus no Oh(ITU hIe (hnn~( in the yigOl of the herhn((ollS Y(gc~ ~l1tion ns jlclgpcl h~ timo wbell pInns stmmiddotted growlh As summnrized m table 23 mcnslIlements of til) basnl H1lJ oj grflsses on n l1lfter quadrut within tll( g-IHzed rnng-c showed thnt theso plnnls deeiined only llhollt 6 PPI((llt in bllsnllllPfI h(tw(PI1 19n nnd 1932 wheleus 011

the four (jIHldlnts on l))ot((tecl rnnglt cllrlier mcntioned the dpdinc in the husnl 111(f1 of glll$B0B during the BHITlC pcgtriod WitS 19 peIcent lllflt gJflscs protce[cd flOtH glHzing should declillc in density ltluring dlough~ YltftIS sueh ItS WNC (xJ)(li(necd dming fhe study pNiod us 11 whole IS (~ompldllH~ible hut why the glt1sses on the glllzed rnngc should during tilt slime prriou dpdinc kss us illdi(llt(d bY the qundshyrilis or eYCgtll Rho lllodpIlItc g-nins flS iudie-ntcd b~r the Stllyey (table 22)J is not so (llsily undllstood All (Xpllll111lioll of jhis nppnlent pnrndox mu~Y be ihn t i il( loss of sng-ebllsh on the grazcd fiTcHlcssPJ1ed til( (olHJ)ltHion for Hynilnbl( Roil moistuI(

TAIlIl 23 Shnllk((f in JlIIml nl((J of JlfIrllldal lr(~~l~ nJ fl rrlrr~rll((1lilC 1nshylm(r 1111(11 pound)ll(trlll in )Illrlrfllrk J rrllll]l(Jrlcl witIL Iwl OJ 1 lIJfrazed glwriro lcwocd on rmlpotuIf lJIJII

(hllu~~s in ulIsrllllr~ frJm W23

Yeur )enr t -[I~ruzed (ugrr17cdOm7rlti 1Jluraltllulruts I qUIldrnts

Prrcnti P(r~cti JI~ 1031 Hl2tL -6 HmiddotI Ul32 j11m -middotj2 +10 IW2J -I -28 Ibrinkoge

~ 57 -~l1I1_10_______ J _ 1

In jew of the ftt(t that hUIlChgrnsscs nnd peI(fIllinl weeds tended to (rowd out inferior shluhs when the heJl)llceous phlllLS were pershymitted to JOo(1I IllntUti(~~ hefolC being grnzcd it would nppenr thnt full grnzing oileIs n pra(ticul method of improving sflgehrllsh~whcu t~ grnss runge lilnds that Imve boeD scriousl)T dtpleted of tihe bettcr iornge plull ts by OYclglflzing flrc or oth( enuses It is recognized thntdefelIcd g1llzing is not a prnctielll system for nll sprillg-fnU 1ange 11l11ds bC(itlllse it uffonls 110 usc of the forage in the spring Howeyer by setting asido suflicicllt neI8uge to (nrry shcep during the spring

19

INclXKXUB OJ GHAZING ON HJgtHlXO-JALJ~ HJj JJ~P HAXOI 35

period deferred use of the rcmuindcr will 0(1 I~ period of yelLrs permit madmuJIl improvement of the Yc~etntioll without any muteshyrial loss of totnl fornge produced

THE SIGIItICANCE OF ItANGE DEPI~TION THltOCGII OVEltGitAZING

In view of the rcsults on these fin~ expcrimcntul arens it is obious thnt nny method of utilization whirh in 11 prriod of g yrurs will rrsult in a reduction of 20 to 65 percent ill the grllzing nlue of the springshyfun range lunds hus no plnce ill II pructieni plan of Illnnngclll(nt for range sh(ep produ(tion In thcfilst pln(c n c(tnin lltllllbcr of she(p cunnot be llluillluin(d sntisfnctoli1y oY(r n J)(Iiod of YNlIS 011 a unit of range while the l(lutiwly pdntabh hrrbu(cous fornge plnlls nr( being lcplneed ill n whol(sulp 111111l11(r by (ornpuratinly llllpnlntnble shrubs lmd othCl plunts Hnngp dppletion of this (hnrnctcr must be met by dmstie redu(fions inthe lltll11b(n of sllPep thut nre gmz(d 011 (Heh unit of rllngr 01 by It (ollrspoJHiing in(J(llse in the runge uerpugr thnt is made nyailable to the snme numbrrs of she(p by ferding hny und grllin to slippiellHnt thr 10ssCs of forllgr or by 11 eombinntiol1 of thCse lllrnsuns nll or wldeh nrp eithCr il11shyprncticnblr or ruinous finllndally In the s((ond pinel the d(InYld growth of forage in the spring on drplp(N llInges as n result of (pshy(pused p]nnt vigor (onstitutrs n furthrr loss in rnnge forflge nt 11

time wlrrn grCPJl frrd is ess(ntid for pwes with young Inmbs This loss cnll bt mct only by furthcr grllzing limitations and in(rensrd (os(s of operntion EYen more discournging is the fnel thflt the possibilitips of improvement by nil t urlll ~ ]p-pgrtn tion f1rr grrn tly dimlnislwd I)(cntlse of the weakrnrci fruit ing hn bil SOl drst Ill (lioIl of desirable r1Jlge plants find bNnusp of the irHICllScd vigor lIlel site dominnll(C of Ie5S clcsia hIe Sl)((hs

Fnfotunntdy (x(rnsiw nrPIlS of spring-fall rungr lunel hn-( been gruzed ycnr IIftpr yrnr in a IIlI1I1lHl (ompurnblr to thr wily in whirh thp four (xpprillwJltnl pnddoks (re utilizltd on the sltrpp stution rungp during the O-ypl1l prriod H)24-~2 und un in nn rycn InOl( 5(riollsly dCplptrd (oncii t ion A sllnry mudr by the Jn trllJ1011ntnin For(st nnd Rung( ]ixpPJinwllt Stntion in H)32 l(-Nded for exnmplp tha t on 842 1](11 yily grnzrd nnd burlwd nlr1S I)(tw(en Wriser lllld Du bois in SOUtiHrJ) Jdn ho til( est ima ted grnzing Ylllllr of the ycgrtnshytion WIIS 802 p(I(cnt IIRS than tht IlYe1ngc yuhr( of the plunt eorr found 011 H)4 nlefls of (ompu1nblc rnllgr lllnds which hlld bcen proshyt((ted 01 tls(d only modellltely for a IOIl~ prJiod of y(n1s rhe dll1sity of the J)llnninl glllsses on the IHayily grllzrd ll1enS wns found to be 835 p(llpnt l(ss thnn on h~htly USN lnngr These Ylllunbl( forngc plants r1p displnrN 011 sornl IHcas by inCl(uRrd Illlmb(rs of sugeshybrush plnnts nlld on otlH1S by nnnllllis of inflliol ~rlzing yulur

Oil muny nllns tl1( Jehrtively ullJlulntnble sngebllrsh hns beeoll1e so drnse thnt lambs nrl lost und J11ueh wool is pull(d from thp sidps nnd bellies of the (w(s while glHzillg thus fUltlwl Jedu(ing til( Ynlu( of thccippkted range fol Wllzing On OOH UrPlIS whrlC the sng(brllsh hus been killed by rrprutd fl~S tie quulity of the 1I11l1uni wg(tation now prpSCIJt is so inf(lior thut muny OptJUtors Ule fOI(ld to suppleshyment the rUllge forngc with hnY lind gluill in oId (I to fnttrn th( Inmbs for IDllrkpt lind to llwintuin the bl(pding stock in thrifty (olldition Rehabilitation of Uj(IlS sHeh ns th(~sc (onstitut(s one of the most importnnt prob](ms needing solution in the est

36 lgUHN1CAJ~ llULLBTlN 600 U H DIWl 01 AGHIUULlUnB

RANGE MAINTENANCE BY CONSERVATIn SPRING AND FALL GRAZING

Although more or less serious dnnlllge occurrcd to the runge cOYer in four of the five cxprriIl1cntnl puddocks undcr systems of glnzing which rcmoYCd purl of the fOlHge in the spring lind plllcticnily nIl of the uvnilublc remaining hNbnecollS vlgetlltion in the faU CII()l yenr observations 011 the herded portion of the Stlltion lnnge show thill under It COllSClU ti ( systcm of glllzing the sngbrush-bunchshyglllss type of (onr (lUI be utilized both ill thc spring and fnIl without serious efrects It is not primarily It qtHstion of (lrly or Jute usc of spring rllnge or of hCUlel glHzill should cOlltinue fOl 2 weeks or 2 mon ths siner rllnge slwp prod uclion lWlliins thn t fOlugn bc uYllilnble during the (ntirc spring s(lIson but it is ruth(r It (jllstion of so IlltcrshylInting usc of cliflenJlt poiliolls of Ileh jt1ng( 1(11 liS to J)Jlclude utilizllshytion of th( sume forllg( plunts during the SHII1t growth stug(~ (ueh y(lIr lind ulso of limiting til( int(nsity of gruzing to gUHrd against overshygrnzing nnd thc yieiHsitudls of (limuL(

In this (onn((tion it has b((11 gelJ(gtrllIly r(cogniz(d that good lttnge mnnng(l11(nt (quir(s tilt ndjustm(nt of lIulllb(rs Ilncl p(riods of usc so thut tIl( (quiyalent of npproximlltely 20 to 25 percent of the forage is l(ft unutiliz(d nt th( (nel of the grnzing S(I1Ron I1S n meltllS of mllintuilling the vigor of the plnnt eOV(I In nddition to this snfeshyguard how(Y(r it is Ilppllr(nt thnt furth(r ndjustlll(nt-either in numbers grnz((1 or periods of us(-is nec(ssnry in ord(I to Illlow for differences in forugc production liS It lcsult of elimntie Jlu(tuntions

In limiting the use of the spring-fall rnng( to insurc mnintenllllce or increuse of pnlatnble lind nourishing fOlng( the clit(rioll must be neither the forllge produCtion of good yenR 1101 of 1Ylruge yenrs While stocking the rnnge on the bnsis of n (HgeYlturs mny be SlttiHshyfacto y on the prlliries as sugglst(d by 8nryis (10) this pructice (1l11l1()t be considered satisfndory ill tIl( intllIl10tlOtnill 1(gion with its gr(nt nonuulllnd plliodi(nL f1uctlutions in prleipitntion In this r(gion the gencrnll(RtIlt hns b((1l thnt in dry ypars more livestock were on the rllnge thun it could support 011 11 sustnin(tl-yield bllsis und before the llumbes of Ilnimals could be r(duc(~d 01 the good yeurs retu1llcd tlte lllng( sufl(lcd It fnr grent(r dlrIine in produdhrity thun slyeral s(llsons of flYllfIge 01 b(tt(r eonditions could restore The serious c1(pletion of mueh of the spring-full runge todny is mute evidence of sueh eOl1s(quln((s nnd ellnrIy suggests the need for improvcd mnnngcmcnt pJu(ti((s which will mnke ndequllte provision for the influencc of fluetuntions in precipitlltion Ilnd other weather fllctors

An example of the Hcessity for such provision is Ilflorded by the record of uvernge IInnulll productlOn of plldtIocks 1 anti 7 lInd the ru te of stociing b((11 s(t to consume on the uvemge not more than 80 percent of the total uvuiInble foJt1ge in Itycrage yellrs (fig 19) a shortshynge of forage involving serious dllmuge to the 1IlIIge would hnve reshysulted in 2 of the 0 y(ars of this study pelioel und in 3 other years less thnn 20 pcrecnt would hllye r(lI1uincd us T(scrve A 20-pcreent surshyplus would have becn J(ft111]925 ]020 1031 und 11)32 only

It is obvious that a safety nlJownnce fOl droughtin ntIdition to a conshyservatiYe degree of foruge utilization in uvcrnge growth yenrs must be applied in arriving nt a long-time lflte of stocking Considering that

INFLUJmCB OF GUAZING ON SPUINd-FALL SHBBP UANGE 37

forage production on the experimental pnddocks varied as much as from 33 percent below to 41 percent above normnl it is clear that in average years a drought allowance of 10 to 20 percent should be added to the utilization allowance of 20 or 25 percent to arrive at a safe rate of stocking if aU overgrazing and supplemental feeding is to be avoided (fig 19)

On the herded portion of thu sagebrush-wheatgrnss range at the United States Sheep Experiment Station the general practice has been to utilize only 60 to 65 percent of the grnsses in average years TIllS basis of utilization has provided for ample forage even in the poorest growth yeaTS and hence has precluded the necessity for supshyplying expensive supplemental feed During the avemge and better years it has permitted the range plants to recovct from the debilishytating effects of intervening drought yeats

TOTAL FORAGE PRODUCTION

PERCENT OF AVERAGE

61---shyIl ~

~

FIGlR lD-A ernge tolal forage protlu(Oon of paddocks 1 nnd i Forage production In In23-l2 varied so greutlmiddot thllt stocking of the range hllsed Oil the u~e of 80 percent of lIvemge fora~e prodUction on theso pndd(cks would havo utilized overy slmp (f forage in 2 of the yellrs nntl brought about n seriollH shortageof feed A furthor allowanltltl for climatic vicissitudes corresponding to the lise of or llerlCut of production would have left no feed shortage ill 1928 and u comfortable margin in other years for building up n greater total production for the future

As is shown in table 24 this range unit of 12377 acres was stocked on the average basis of about 20 sheep-days pel acre or 1~ acres per head per month for two periods of approximately 2~ months each in the spring and fall resulting in the utilization on an avernge of 65 percent of the bunchgmss forage annually

Under this system of grazing and rate of stocking adequate forage was available for the sheep in all years in the spring as well as in the fall For example observations made late in the fall each yellr reshyvealed that never WllFl more than 85 percen t of the bunchgmsses utilizcd evcn in the poor years of 1924 1926 and 1928 when growth was short In years of comparotively luxllliant growth such as 1925 and 1932 these gmsses were gJfLzcd only 50 percent or less This unit was grazed on a rotation plILn whereby in the spring of one yellr the sheep were routed over the area in one diIection and the next year

38 TEOHNICAlJ nUUmiddot1TlN 600 U S DBPT Ol AGRIOUIJTUHB

in a different direction beginning each spring about the time the grasses appronched 2-inch height growth and ending at the close of the growing season on about June 25 In this manner the portion of the range grazed enrly in one year was not grazed until late in the spring of the next yeur when vegetation had renched full developshyment A similar rotation system of herding wus followed in the fall in most years beginning about September 15 and ending about Deshycember 1 During the period as 11 whole spring and fall grazing were about equally heavy

lABfB 24-Act1wl lise 111der conservative ~pring and faIl1l~e of 12877 acres of the United 8tate~ Sheep RxpIJIiment 8talion range slocked at the raie of 20 ~ltc(7)shyda1ls per flcre 01 flPPlorilllleli JIt ((I(N per head 1)er month jor 5 1lumths 194-I2

Spring Ilruzlllg Full grnzllll( I Y(llrl~ lntnl 1~tImiddot _ _ bull _bullbull____ bull ____ bull__ lJIute1

I lolillYeor

I I~p rIFor-I lso of IJI~r Usc of Il~ CorngoPuriwJ or use 1 ~JI u~o Imiddoteri1 of 1Jij rU1gc H~O rungo n~u producshyru II I wa~d bull used ustld lion I I I----1------ -----1middot- i-- ------~--shy

S(rel Shrel Shet S(eep rluV Prrmiddot tlav Permiddot tillY Permiddot till Vii

per tlat uul per urre cen per (Jlre [cnl per acre Jl2-i ____ bull - ]-[Ir 28-Jllno 20bullbull 1107 M SCIItI[-NomiddotI 0711 11 18W 85 211)0 1025 prO-JuIIl12Ubull laa1 H ScpL2l-J)eCI1 028 Ifl WU2 50 192middot1 W2U _ Apl12-Jllllo28 bullbull 1177 1-1 iieptJU-Dcc HI 1740 51 ~~J17 86 Hl2 1927 _ bullbull _ Apr12-Jul~ 10 1155 middot11 HeptlJ-lJ~cO __ bull 871 12 2U20 7[ 27UI W28 ___ _ Apr17-Jullc2L_ JI)88 1U Sept15-)cc bullbullbull 1227 JJ 211( MI 2781 192U__ ____ Apr18-June2L 1102 au Sepl2U-Nov2U (jn 24 lin lIal 2S21 WSO Apr 14-Jullc 18 bull I) IU 21 Supt 12-Nov III 1051 a5 Ill iO 511 l 2082 1911 _ __ 1AprlI-JulluHI fl 11 IS Aug2r-NovHIbullbull 1214 a7 IHr7 551 aa70 1912 _ Apr2a-Juuo27_ 4[U J1 $cptIl)-Dce12 781 23 I 40 l7 aafoJ

Aerago Apr la-JUliO 211 UJ7(7i21 Sepl IH)ee 2 __ fi88- --3lI-IIJ55 -M--Ulili

l I~~tilllutlltilotlil fnrage prmlucllllll (~hecpmiddottlnys pcr Iltrc) uvorugo 112-1--25 1tl42j II11-a2 latH (111111 III (orutl ~allle bolwcnn 1I1-2i ulHl lUU-i2 11 l)crccn

I computed IIverages SeofootnoloJIII)

SYfltmnntic measllIements of the vegetation were not mude ovcr tho herded portion of the stntion 1Ilnge although geneml observntions ns well as the grl1zing rceord indieate that the rtlnge cover hus I~een mnintnined from yetlr to yenl in 11 high stnge of productivity Ji or cxnmple when the nmnbel of sheep-dl1Ys use per ncre for each yelLl iB weighted hy the degree to which the bunchgrl1sses were utilized the estimnted feed per nere of this clnss of fomge increased from ILn I1vc1llge of 30 sheep-days for the 2-yenr period 1924~25 to (LIl nverllge of 34 during the Inst 2 years of the 9-year period 01 nn increase for the period of nbou t 11 percen t This increase in productivity is considered especinlly significnnt in view of the genell111y unfavornble climatic conditions which prevniled during the study period

On ranges in reasonably good condition chnrtlcterized by a plant oover of 25 percent density comprising 45 percent of bunch~lfiss and pulatnble weed and 55 percent of less pnl1tnble shrubs tIllS system nnd degree of spring and fnllutilization is well adnpted to the requireshyments of range sheep production It provides feed nt an enrly date in the spring aIld I1n adequll te supply of cured forage in the fnll I1ml climinntes grazing on the identicuimnge unit I1t the same time each yenr Moreover stocking to nllow n surplus of feed on the ground in normal years flssurcs it full-length grnzing senson in dry yeurs In

36 lgUHN1CAJ~ llULLBTlN 600 U H DIWl 01 AGHIUULlUnB

RANGE MAINTENANCE BY CONSERVATIn SPRING AND FALL GRAZING

Although more or less serious dnnlllge occurrcd to the runge cOYer in four of the five cxprriIl1cntnl puddocks undcr systems of glnzing which rcmoYCd purl of the fOlHge in the spring lind plllcticnily nIl of the uvnilublc remaining hNbnecollS vlgetlltion in the faU CII()l yenr observations 011 the herded portion of the Stlltion lnnge show thill under It COllSClU ti ( systcm of glllzing the sngbrush-bunchshyglllss type of (onr (lUI be utilized both ill thc spring and fnIl without serious efrects It is not primarily It qtHstion of (lrly or Jute usc of spring rllnge or of hCUlel glHzill should cOlltinue fOl 2 weeks or 2 mon ths siner rllnge slwp prod uclion lWlliins thn t fOlugn bc uYllilnble during the (ntirc spring s(lIson but it is ruth(r It (jllstion of so IlltcrshylInting usc of cliflenJlt poiliolls of Ileh jt1ng( 1(11 liS to J)Jlclude utilizllshytion of th( sume forllg( plunts during the SHII1t growth stug(~ (ueh y(lIr lind ulso of limiting til( int(nsity of gruzing to gUHrd against overshygrnzing nnd thc yieiHsitudls of (limuL(

In this (onn((tion it has b((11 gelJ(gtrllIly r(cogniz(d that good lttnge mnnng(l11(nt (quir(s tilt ndjustm(nt of lIulllb(rs Ilncl p(riods of usc so thut tIl( (quiyalent of npproximlltely 20 to 25 percent of the forage is l(ft unutiliz(d nt th( (nel of the grnzing S(I1Ron I1S n meltllS of mllintuilling the vigor of the plnnt eOV(I In nddition to this snfeshyguard how(Y(r it is Ilppllr(nt thnt furth(r ndjustlll(nt-either in numbers grnz((1 or periods of us(-is nec(ssnry in ord(I to Illlow for differences in forugc production liS It lcsult of elimntie Jlu(tuntions

In limiting the use of the spring-fall rnng( to insurc mnintenllllce or increuse of pnlatnble lind nourishing fOlng( the clit(rioll must be neither the forllge produCtion of good yenR 1101 of 1Ylruge yenrs While stocking the rnnge on the bnsis of n (HgeYlturs mny be SlttiHshyfacto y on the prlliries as sugglst(d by 8nryis (10) this pructice (1l11l1()t be considered satisfndory ill tIl( intllIl10tlOtnill 1(gion with its gr(nt nonuulllnd plliodi(nL f1uctlutions in prleipitntion In this r(gion the gencrnll(RtIlt hns b((1l thnt in dry ypars more livestock were on the rllnge thun it could support 011 11 sustnin(tl-yield bllsis und before the llumbes of Ilnimals could be r(duc(~d 01 the good yeurs retu1llcd tlte lllng( sufl(lcd It fnr grent(r dlrIine in produdhrity thun slyeral s(llsons of flYllfIge 01 b(tt(r eonditions could restore The serious c1(pletion of mueh of the spring-full runge todny is mute evidence of sueh eOl1s(quln((s nnd ellnrIy suggests the need for improvcd mnnngcmcnt pJu(ti((s which will mnke ndequllte provision for the influencc of fluetuntions in precipitlltion Ilnd other weather fllctors

An example of the Hcessity for such provision is Ilflorded by the record of uvernge IInnulll productlOn of plldtIocks 1 anti 7 lInd the ru te of stociing b((11 s(t to consume on the uvemge not more than 80 percent of the total uvuiInble foJt1ge in Itycrage yellrs (fig 19) a shortshynge of forage involving serious dllmuge to the 1IlIIge would hnve reshysulted in 2 of the 0 y(ars of this study pelioel und in 3 other years less thnn 20 pcrecnt would hllye r(lI1uincd us T(scrve A 20-pcreent surshyplus would have becn J(ft111]925 ]020 1031 und 11)32 only

It is obvious that a safety nlJownnce fOl droughtin ntIdition to a conshyservatiYe degree of foruge utilization in uvcrnge growth yenrs must be applied in arriving nt a long-time lflte of stocking Considering that

INFLUJmCB OF GUAZING ON SPUINd-FALL SHBBP UANGE 37

forage production on the experimental pnddocks varied as much as from 33 percent below to 41 percent above normnl it is clear that in average years a drought allowance of 10 to 20 percent should be added to the utilization allowance of 20 or 25 percent to arrive at a safe rate of stocking if aU overgrazing and supplemental feeding is to be avoided (fig 19)

On the herded portion of thu sagebrush-wheatgrnss range at the United States Sheep Experiment Station the general practice has been to utilize only 60 to 65 percent of the grnsses in average years TIllS basis of utilization has provided for ample forage even in the poorest growth yeaTS and hence has precluded the necessity for supshyplying expensive supplemental feed During the avemge and better years it has permitted the range plants to recovct from the debilishytating effects of intervening drought yeats

TOTAL FORAGE PRODUCTION

PERCENT OF AVERAGE

61---shyIl ~

~

FIGlR lD-A ernge tolal forage protlu(Oon of paddocks 1 nnd i Forage production In In23-l2 varied so greutlmiddot thllt stocking of the range hllsed Oil the u~e of 80 percent of lIvemge fora~e prodUction on theso pndd(cks would havo utilized overy slmp (f forage in 2 of the yellrs nntl brought about n seriollH shortageof feed A furthor allowanltltl for climatic vicissitudes corresponding to the lise of or llerlCut of production would have left no feed shortage ill 1928 and u comfortable margin in other years for building up n greater total production for the future

As is shown in table 24 this range unit of 12377 acres was stocked on the average basis of about 20 sheep-days pel acre or 1~ acres per head per month for two periods of approximately 2~ months each in the spring and fall resulting in the utilization on an avernge of 65 percent of the bunchgmss forage annually

Under this system of grazing and rate of stocking adequate forage was available for the sheep in all years in the spring as well as in the fall For example observations made late in the fall each yellr reshyvealed that never WllFl more than 85 percen t of the bunchgmsses utilizcd evcn in the poor years of 1924 1926 and 1928 when growth was short In years of comparotively luxllliant growth such as 1925 and 1932 these gmsses were gJfLzcd only 50 percent or less This unit was grazed on a rotation plILn whereby in the spring of one yellr the sheep were routed over the area in one diIection and the next year

38 TEOHNICAlJ nUUmiddot1TlN 600 U S DBPT Ol AGRIOUIJTUHB

in a different direction beginning each spring about the time the grasses appronched 2-inch height growth and ending at the close of the growing season on about June 25 In this manner the portion of the range grazed enrly in one year was not grazed until late in the spring of the next yeur when vegetation had renched full developshyment A similar rotation system of herding wus followed in the fall in most years beginning about September 15 and ending about Deshycember 1 During the period as 11 whole spring and fall grazing were about equally heavy

lABfB 24-Act1wl lise 111der conservative ~pring and faIl1l~e of 12877 acres of the United 8tate~ Sheep RxpIJIiment 8talion range slocked at the raie of 20 ~ltc(7)shyda1ls per flcre 01 flPPlorilllleli JIt ((I(N per head 1)er month jor 5 1lumths 194-I2

Spring Ilruzlllg Full grnzllll( I Y(llrl~ lntnl 1~tImiddot _ _ bull _bullbull____ bull ____ bull__ lJIute1

I lolillYeor

I I~p rIFor-I lso of IJI~r Usc of Il~ CorngoPuriwJ or use 1 ~JI u~o Imiddoteri1 of 1Jij rU1gc H~O rungo n~u producshyru II I wa~d bull used ustld lion I I I----1------ -----1middot- i-- ------~--shy

S(rel Shrel Shet S(eep rluV Prrmiddot tlav Permiddot tillY Permiddot till Vii

per tlat uul per urre cen per (Jlre [cnl per acre Jl2-i ____ bull - ]-[Ir 28-Jllno 20bullbull 1107 M SCIItI[-NomiddotI 0711 11 18W 85 211)0 1025 prO-JuIIl12Ubull laa1 H ScpL2l-J)eCI1 028 Ifl WU2 50 192middot1 W2U _ Apl12-Jllllo28 bullbull 1177 1-1 iieptJU-Dcc HI 1740 51 ~~J17 86 Hl2 1927 _ bullbull _ Apr12-Jul~ 10 1155 middot11 HeptlJ-lJ~cO __ bull 871 12 2U20 7[ 27UI W28 ___ _ Apr17-Jullc2L_ JI)88 1U Sept15-)cc bullbullbull 1227 JJ 211( MI 2781 192U__ ____ Apr18-June2L 1102 au Sepl2U-Nov2U (jn 24 lin lIal 2S21 WSO Apr 14-Jullc 18 bull I) IU 21 Supt 12-Nov III 1051 a5 Ill iO 511 l 2082 1911 _ __ 1AprlI-JulluHI fl 11 IS Aug2r-NovHIbullbull 1214 a7 IHr7 551 aa70 1912 _ Apr2a-Juuo27_ 4[U J1 $cptIl)-Dce12 781 23 I 40 l7 aafoJ

Aerago Apr la-JUliO 211 UJ7(7i21 Sepl IH)ee 2 __ fi88- --3lI-IIJ55 -M--Ulili

l I~~tilllutlltilotlil fnrage prmlucllllll (~hecpmiddottlnys pcr Iltrc) uvorugo 112-1--25 1tl42j II11-a2 latH (111111 III (orutl ~allle bolwcnn 1I1-2i ulHl lUU-i2 11 l)crccn

I computed IIverages SeofootnoloJIII)

SYfltmnntic measllIements of the vegetation were not mude ovcr tho herded portion of the stntion 1Ilnge although geneml observntions ns well as the grl1zing rceord indieate that the rtlnge cover hus I~een mnintnined from yetlr to yenl in 11 high stnge of productivity Ji or cxnmple when the nmnbel of sheep-dl1Ys use per ncre for each yelLl iB weighted hy the degree to which the bunchgrl1sses were utilized the estimnted feed per nere of this clnss of fomge increased from ILn I1vc1llge of 30 sheep-days for the 2-yenr period 1924~25 to (LIl nverllge of 34 during the Inst 2 years of the 9-year period 01 nn increase for the period of nbou t 11 percen t This increase in productivity is considered especinlly significnnt in view of the genell111y unfavornble climatic conditions which prevniled during the study period

On ranges in reasonably good condition chnrtlcterized by a plant oover of 25 percent density comprising 45 percent of bunch~lfiss and pulatnble weed and 55 percent of less pnl1tnble shrubs tIllS system nnd degree of spring and fnllutilization is well adnpted to the requireshyments of range sheep production It provides feed nt an enrly date in the spring aIld I1n adequll te supply of cured forage in the fnll I1ml climinntes grazing on the identicuimnge unit I1t the same time each yenr Moreover stocking to nllow n surplus of feed on the ground in normal years flssurcs it full-length grnzing senson in dry yeurs In

INFLUJmCB OF GUAZING ON SPUINd-FALL SHBBP UANGE 37

forage production on the experimental pnddocks varied as much as from 33 percent below to 41 percent above normnl it is clear that in average years a drought allowance of 10 to 20 percent should be added to the utilization allowance of 20 or 25 percent to arrive at a safe rate of stocking if aU overgrazing and supplemental feeding is to be avoided (fig 19)

On the herded portion of thu sagebrush-wheatgrnss range at the United States Sheep Experiment Station the general practice has been to utilize only 60 to 65 percent of the grnsses in average years TIllS basis of utilization has provided for ample forage even in the poorest growth yeaTS and hence has precluded the necessity for supshyplying expensive supplemental feed During the avemge and better years it has permitted the range plants to recovct from the debilishytating effects of intervening drought yeats

TOTAL FORAGE PRODUCTION

PERCENT OF AVERAGE

61---shyIl ~

~

FIGlR lD-A ernge tolal forage protlu(Oon of paddocks 1 nnd i Forage production In In23-l2 varied so greutlmiddot thllt stocking of the range hllsed Oil the u~e of 80 percent of lIvemge fora~e prodUction on theso pndd(cks would havo utilized overy slmp (f forage in 2 of the yellrs nntl brought about n seriollH shortageof feed A furthor allowanltltl for climatic vicissitudes corresponding to the lise of or llerlCut of production would have left no feed shortage ill 1928 and u comfortable margin in other years for building up n greater total production for the future

As is shown in table 24 this range unit of 12377 acres was stocked on the average basis of about 20 sheep-days pel acre or 1~ acres per head per month for two periods of approximately 2~ months each in the spring and fall resulting in the utilization on an avernge of 65 percent of the bunchgmss forage annually

Under this system of grazing and rate of stocking adequate forage was available for the sheep in all years in the spring as well as in the fall For example observations made late in the fall each yellr reshyvealed that never WllFl more than 85 percen t of the bunchgmsses utilizcd evcn in the poor years of 1924 1926 and 1928 when growth was short In years of comparotively luxllliant growth such as 1925 and 1932 these gmsses were gJfLzcd only 50 percent or less This unit was grazed on a rotation plILn whereby in the spring of one yellr the sheep were routed over the area in one diIection and the next year

38 TEOHNICAlJ nUUmiddot1TlN 600 U S DBPT Ol AGRIOUIJTUHB

in a different direction beginning each spring about the time the grasses appronched 2-inch height growth and ending at the close of the growing season on about June 25 In this manner the portion of the range grazed enrly in one year was not grazed until late in the spring of the next yeur when vegetation had renched full developshyment A similar rotation system of herding wus followed in the fall in most years beginning about September 15 and ending about Deshycember 1 During the period as 11 whole spring and fall grazing were about equally heavy

lABfB 24-Act1wl lise 111der conservative ~pring and faIl1l~e of 12877 acres of the United 8tate~ Sheep RxpIJIiment 8talion range slocked at the raie of 20 ~ltc(7)shyda1ls per flcre 01 flPPlorilllleli JIt ((I(N per head 1)er month jor 5 1lumths 194-I2

Spring Ilruzlllg Full grnzllll( I Y(llrl~ lntnl 1~tImiddot _ _ bull _bullbull____ bull ____ bull__ lJIute1

I lolillYeor

I I~p rIFor-I lso of IJI~r Usc of Il~ CorngoPuriwJ or use 1 ~JI u~o Imiddoteri1 of 1Jij rU1gc H~O rungo n~u producshyru II I wa~d bull used ustld lion I I I----1------ -----1middot- i-- ------~--shy

S(rel Shrel Shet S(eep rluV Prrmiddot tlav Permiddot tillY Permiddot till Vii

per tlat uul per urre cen per (Jlre [cnl per acre Jl2-i ____ bull - ]-[Ir 28-Jllno 20bullbull 1107 M SCIItI[-NomiddotI 0711 11 18W 85 211)0 1025 prO-JuIIl12Ubull laa1 H ScpL2l-J)eCI1 028 Ifl WU2 50 192middot1 W2U _ Apl12-Jllllo28 bullbull 1177 1-1 iieptJU-Dcc HI 1740 51 ~~J17 86 Hl2 1927 _ bullbull _ Apr12-Jul~ 10 1155 middot11 HeptlJ-lJ~cO __ bull 871 12 2U20 7[ 27UI W28 ___ _ Apr17-Jullc2L_ JI)88 1U Sept15-)cc bullbullbull 1227 JJ 211( MI 2781 192U__ ____ Apr18-June2L 1102 au Sepl2U-Nov2U (jn 24 lin lIal 2S21 WSO Apr 14-Jullc 18 bull I) IU 21 Supt 12-Nov III 1051 a5 Ill iO 511 l 2082 1911 _ __ 1AprlI-JulluHI fl 11 IS Aug2r-NovHIbullbull 1214 a7 IHr7 551 aa70 1912 _ Apr2a-Juuo27_ 4[U J1 $cptIl)-Dce12 781 23 I 40 l7 aafoJ

Aerago Apr la-JUliO 211 UJ7(7i21 Sepl IH)ee 2 __ fi88- --3lI-IIJ55 -M--Ulili

l I~~tilllutlltilotlil fnrage prmlucllllll (~hecpmiddottlnys pcr Iltrc) uvorugo 112-1--25 1tl42j II11-a2 latH (111111 III (orutl ~allle bolwcnn 1I1-2i ulHl lUU-i2 11 l)crccn

I computed IIverages SeofootnoloJIII)

SYfltmnntic measllIements of the vegetation were not mude ovcr tho herded portion of the stntion 1Ilnge although geneml observntions ns well as the grl1zing rceord indieate that the rtlnge cover hus I~een mnintnined from yetlr to yenl in 11 high stnge of productivity Ji or cxnmple when the nmnbel of sheep-dl1Ys use per ncre for each yelLl iB weighted hy the degree to which the bunchgrl1sses were utilized the estimnted feed per nere of this clnss of fomge increased from ILn I1vc1llge of 30 sheep-days for the 2-yenr period 1924~25 to (LIl nverllge of 34 during the Inst 2 years of the 9-year period 01 nn increase for the period of nbou t 11 percen t This increase in productivity is considered especinlly significnnt in view of the genell111y unfavornble climatic conditions which prevniled during the study period

On ranges in reasonably good condition chnrtlcterized by a plant oover of 25 percent density comprising 45 percent of bunch~lfiss and pulatnble weed and 55 percent of less pnl1tnble shrubs tIllS system nnd degree of spring and fnllutilization is well adnpted to the requireshyments of range sheep production It provides feed nt an enrly date in the spring aIld I1n adequll te supply of cured forage in the fnll I1ml climinntes grazing on the identicuimnge unit I1t the same time each yenr Moreover stocking to nllow n surplus of feed on the ground in normal years flssurcs it full-length grnzing senson in dry yeurs In

38 TEOHNICAlJ nUUmiddot1TlN 600 U S DBPT Ol AGRIOUIJTUHB

in a different direction beginning each spring about the time the grasses appronched 2-inch height growth and ending at the close of the growing season on about June 25 In this manner the portion of the range grazed enrly in one year was not grazed until late in the spring of the next yeur when vegetation had renched full developshyment A similar rotation system of herding wus followed in the fall in most years beginning about September 15 and ending about Deshycember 1 During the period as 11 whole spring and fall grazing were about equally heavy

lABfB 24-Act1wl lise 111der conservative ~pring and faIl1l~e of 12877 acres of the United 8tate~ Sheep RxpIJIiment 8talion range slocked at the raie of 20 ~ltc(7)shyda1ls per flcre 01 flPPlorilllleli JIt ((I(N per head 1)er month jor 5 1lumths 194-I2

Spring Ilruzlllg Full grnzllll( I Y(llrl~ lntnl 1~tImiddot _ _ bull _bullbull____ bull ____ bull__ lJIute1

I lolillYeor

I I~p rIFor-I lso of IJI~r Usc of Il~ CorngoPuriwJ or use 1 ~JI u~o Imiddoteri1 of 1Jij rU1gc H~O rungo n~u producshyru II I wa~d bull used ustld lion I I I----1------ -----1middot- i-- ------~--shy

S(rel Shrel Shet S(eep rluV Prrmiddot tlav Permiddot tillY Permiddot till Vii

per tlat uul per urre cen per (Jlre [cnl per acre Jl2-i ____ bull - ]-[Ir 28-Jllno 20bullbull 1107 M SCIItI[-NomiddotI 0711 11 18W 85 211)0 1025 prO-JuIIl12Ubull laa1 H ScpL2l-J)eCI1 028 Ifl WU2 50 192middot1 W2U _ Apl12-Jllllo28 bullbull 1177 1-1 iieptJU-Dcc HI 1740 51 ~~J17 86 Hl2 1927 _ bullbull _ Apr12-Jul~ 10 1155 middot11 HeptlJ-lJ~cO __ bull 871 12 2U20 7[ 27UI W28 ___ _ Apr17-Jullc2L_ JI)88 1U Sept15-)cc bullbullbull 1227 JJ 211( MI 2781 192U__ ____ Apr18-June2L 1102 au Sepl2U-Nov2U (jn 24 lin lIal 2S21 WSO Apr 14-Jullc 18 bull I) IU 21 Supt 12-Nov III 1051 a5 Ill iO 511 l 2082 1911 _ __ 1AprlI-JulluHI fl 11 IS Aug2r-NovHIbullbull 1214 a7 IHr7 551 aa70 1912 _ Apr2a-Juuo27_ 4[U J1 $cptIl)-Dce12 781 23 I 40 l7 aafoJ

Aerago Apr la-JUliO 211 UJ7(7i21 Sepl IH)ee 2 __ fi88- --3lI-IIJ55 -M--Ulili

l I~~tilllutlltilotlil fnrage prmlucllllll (~hecpmiddottlnys pcr Iltrc) uvorugo 112-1--25 1tl42j II11-a2 latH (111111 III (orutl ~allle bolwcnn 1I1-2i ulHl lUU-i2 11 l)crccn

I computed IIverages SeofootnoloJIII)

SYfltmnntic measllIements of the vegetation were not mude ovcr tho herded portion of the stntion 1Ilnge although geneml observntions ns well as the grl1zing rceord indieate that the rtlnge cover hus I~een mnintnined from yetlr to yenl in 11 high stnge of productivity Ji or cxnmple when the nmnbel of sheep-dl1Ys use per ncre for each yelLl iB weighted hy the degree to which the bunchgrl1sses were utilized the estimnted feed per nere of this clnss of fomge increased from ILn I1vc1llge of 30 sheep-days for the 2-yenr period 1924~25 to (LIl nverllge of 34 during the Inst 2 years of the 9-year period 01 nn increase for the period of nbou t 11 percen t This increase in productivity is considered especinlly significnnt in view of the genell111y unfavornble climatic conditions which prevniled during the study period

On ranges in reasonably good condition chnrtlcterized by a plant oover of 25 percent density comprising 45 percent of bunch~lfiss and pulatnble weed and 55 percent of less pnl1tnble shrubs tIllS system nnd degree of spring and fnllutilization is well adnpted to the requireshyments of range sheep production It provides feed nt an enrly date in the spring aIld I1n adequll te supply of cured forage in the fnll I1ml climinntes grazing on the identicuimnge unit I1t the same time each yenr Moreover stocking to nllow n surplus of feed on the ground in normal years flssurcs it full-length grnzing senson in dry yeurs In

INFLUENOE OF GRAZING ON SPRING-FALL Hlmp RANGE 39

wet years many plants have a chance to reach maturity before being grazed and thereby to recover from previous severe drought

The rate of stocking applied in this rotation plan on this particular range may not apply to other ranges because of differences in the kind and amount of fmage that may be available Regardless however of the productivitv of the range it is highly essential that the influence of climate be recognized and thnt the bDsic rate of stocking include a margin of safety against the vicissitudes of drought Successful manshyagement of the spring-fall type of range therefore necessitates a careful evaluation of the influence of elimate on forage production as well as a recognition that the nbility of forage plan ts to withstand gmzing is limited

SUMMARY AND CONCLUSIONS

The influence of climate and grazing on (1) the periods of range use (2) forage production and (3) the condition ond yields of range sheep was investigated at the United States Sheep Experiment Station neal Dubois Idaho during the period 1924-32 The studim yielded the following results

Spring-fall range lands in southern IdiLho are subject to wide flucshytuations of climate from year to year

Monthly meitn temperatures runged from 17G9deg F in January to 6936 0 in July while duily extremes as low ns -26 0 occurred in Janshyuary and as high ns 1020 in July On the nverage temperatures reshymained above 40 0 from April 10 to October 20 01 a period of 193 days

Precipitation uveriLged 1018 inches annually 438 inches of which occurred itS snow and rnin dming the 6-Ulonth period October 1 to March 31 It is subject to wide fluctuations from yenr to year and from month to month Rainfall is palticulmly uncertain during theshyspring und summer months rainless periods often permitting the soil to become thoroughly dry for weeks at n time after June The maxishymum annual precipitfLtion Wtts 1666 inches and the minimum 600 inches During the 9-year period 2 yenrs were above averiLge 3 were nbout averuge nnd 4 distinctly below averflge

Whell oompnred with recorcls nt Idaho Falls 50 miles distant it is evident thfLt precipibation dLUing the 9-yeal period of study WllS about 16 percent below normal and that the period of study wns pnrt of the longest of seveml dry cycles on record for thnt section

The ann ual fl tlctuntions in weather resulted in illl portnn t changes in the amount of forage produced thus directly nfJeeting the periods of use the grazing cnpacity of the range aLid to some extent the condition and productivity of sheep

The start of fomge growth in the spring varied from as enrly as March 20 to llS lnte as April 24 01 a range of 3G days Imgely llS the result of fluctul1tions in the time at which tempemtliles rose to levels favorable for plunt growth

Two-inch height growth wus reached on the approximate average date of April 22 and was subject to a range 01 only 18 days between the earliest and latest dates fLIso Inlgely due to fluctuations in temperature

Four- and six-inch stages of height growth seed formation and clUing v1ried in OCClUrence with respect to the eaLliest alld latest date during the study period by 27 37 60 and 56 dttys respectively

40 TECHNICAL BULLETIN 600 U S DEPT Ol~ AGRTCULTUUE

partly due to temperature but more especially to differences III

precipitation The volume of forage produced varied from 41 percent above to

33 percent below the 9-year average largely as the result of preshycipitation during the winter and spring season

The basal area of perennial grasses on protected quadrats declined 19 percent dwing the period 1923-32 owing to the breaking up of large clumps following drought

Livestock condition and yields appeared to pounductuate in accordance with general range conditions but other elements induding improveshyment by selection and breeding the maintenance of the sheep in generally high condition at all times and the condition to which the sheep were subjected on the summer and winter range and winter feed lots tended to obscure the specific influence of climate dming the spring and fr11 seasons The most striking relationships indicated that body weights of sheep were purtially af1ected by both spring and fall range conditions and the number of lambs born alive WllS influenced by climatic conditions of the preceding year

Over and above the influence of climate the intensity and periods of gfflzing had a profOlffid effect upon the grazing value of the springshyfuU range

Serious range depletion occurred on four 80-acre range areas where for 9 years from 19 to 68 percent of the available forage was utilized in the spring followed by the removal of from 25 to 66 percent of the forage in the fall or a total for the year of 82 to 93 percent The degree of depletion on the four ranges was applOimately directly proportional to the intensity of spring use 11easumble effects of overgrazing ineluded the reduetion of from 20 to 05 percent in grnzing value an increase of 27 to 73 percent in the density of relatively unpnlatuble sagebrush and other shrubs a decrease of 14 to 81 pershycent in the density of highly palatable weeds and bUl1chgrasses and a delay of as many as 14 days in the occurrence of 2-inch 11eight growth of grasses and diminished weed-flower production due to decreased vigor

011 another 80-acre range area on which on the average 83 pereent of all aVililable fOTage WitS utilized in the fall and none in the spring the range del1nitely improved This improvement was chameterized by an increase of 15 percent 111 grnzmg vnlue it 15- and 16-pelcent irerease in the density of grass and weed forage respeetively and a 5-percent decrease in the denSIty of sagebrush and other shrubs

The herded portion of the station range WitS maintained in a proshyclueti e condition when grazed flccording to a rotation system whereby in average years approximntely 30 to 35 percent of the available bUllchgrasses were utilized in the spring stflrting when the grasses approflched 2-inch height growth and about 33 percent in the fall 01 up to 65 pelcentfor the year flS a wbole For the 9-yCllr period this range was used at the rate of about ]~ aeres pel sheep pel month for approximately 2X mon ths in the spring flncl in the lall

From these results the following conclusions are drawn with respect to proper periods of mnge use the rate of stocking and systems of grazing for range sheep nULllilgement on spling-fnllll1l1ges in southern Idahocharacterizecl by sagebrush-bunchgmss vegetation

1 The yenrly ealendnl of operations should be phtnlled so as to begin spring grazing after grasses reach 2-illeh height Orowth There is a minimum of yariation in this stage of development thus insuring available fornge in most yeurs and necessitating the maintenance of not more than a lO-clny supply of reserve feed for the exceptional year when fomge development is IILte This also precludes misuse of the range since from this time on forage groth will orditlllrily profess in advance of the sheep insUJing that ndequate feed will be available during the entire spring season if the range is not overshystocked Near Dubois Idaho 2-inch height growth is reached on the appro~-imate average date of April 22 Spring gmzing should end when bunchgrasses begin to cure which occms about Tllly 2 near Dubois

2 Full grf1zing should bei-gt111 wben summer runge is utilized but preferu bly nrter ruins sturt regrowth 01 grnsses or soften the cured bunchgrHsses Since fall grazing must end with the comillg of deep suow and this ocell1Ienee is extremel~T vmiable R 30-day reserve supply of feed or its equivalent 01 protected winter range over nnd aboe normal winter requirements should be lluulltailled as instuance against yenrs of enrly snows

3 For ranges hllwg a totnl plant (oyer of nbout 25 percent comshyprising approximately 45 per(ent of bunchgrnsses lInd palatable weeds and 55 percen t of sngeblush and 0 t her less pula til bIe shru bs stocking should be at the rute of two-thirds of a sheep pCI acre per month for approxinwtely 2Yz months in the spring nnd in the full A lower rnte of stocking is recommended where Jeluti-ely less bunchshygmss and weed fornge is nnliln ble tlnd a hig]1(r rute on Hrens supportshying a more dense stand of palatable vegetation

4 Rotation SPling gmzing is essentinl for mnintnining sagebrllshshybunchgrass rnnge under the couditions of (limate which preYnii in this section This systcm clln be npplied bT diyiding the mnge into two or more convenient uuits ilud routing the sbeep frOlll one to the other as the senson ndvnuces beginning this process with a different unit each succeeding yenr The periods of use and Tilte of sto(king should be ndj usted so tbn t nppro-illlut(ly one-third of the available bunchgrasses oyer the range ns n whok nre utilized during the spring season ufter grasses Teach 2-in(h height growth and not to exceed two-thirds of the total in the fall of aycrnge growth yeHrs This sysshytem of munugement willlIlsUle adequate forage in the poorest grOvth year and in good years will permit rnnge plants which mny hue been heasily grazed in prevJOus yeurs of drought to recover vigor ~[oreshyover because ample foruge is available under tbis system the sheep cau be expected to be maintained in a thrifty alld productive condition

5 Deferring nIl grnzing Ull til fall for a period of seycnd yeurs on successive portions of the range is recommended for obtaining maxishymum improvement of depleted range

42 TECJlNlUAL BIJLLErlN 600 U S DEPT Ol AGlUUIJLTUR1~

(1)

(2)

(3)

(4)

(51

(6)

(71

(fl)

(10i

LITERATURE CITED

COOPER r M Ilnd STOEHlt 1 A 1934 COMIAIUSOX OP ItAMBOUlLLIT COlmnDALE AXD COLUMBIA SHEEP

UXDJm lXTgRMOeXTAlX HAXla COXDITIONS l S Dept Agr Cire 308 16 pp ilIus

1OHSLIXO C L Ilnd STOUlII Eo V 1929 rlll CTIIIZATIOX OF IIllOSl JoOltAGI~ S HUMMlm RAXCH ]oOR

GAlTIm IX SOUTHWJSTERX U1AII t H Dept Agr Gire 62 30 pp ilIus

AHDlX] f 1 and ANDEHSON M 1919 HANGE MANAGIMEXT ON TUE NA 110 NAl FUHI~HIH C H Dept

A~r Bull 790 98 pp illus --- une FousrlxG G L

1922 RANGE AXD GATlLI~ MANAOIM IXT Dl1UQ DI(()tTUIIT U S Dept Agr Bull 103 84 ppbull LIlus

MeGA ftl E G 1937 Till lULATION (W GltoWIII 10 1111 AItYIN( (AHBlJIIYDltAT1 CUXshy

1gX~1 IN M()lNTAIX J11~OME GltASS l S Dept Agr Tech Bull 598 24 ]lp illus

NJoISON Eo 1934 rilE lXFLVEXCE 01 IUlClll1AlION AXD GltAUNG UPON BLACK

(tAMA OItASS HAXG1 L H DeJlt Agr Tech BuLl 409 32 pp illus

SAMIHOX A W 1918 CLllllAlI AXD l IA WI GIWWTll IN CEHlA1X VEGJTAIIVB ASSOCIAshy

TIONf LT H Dept A~r Bull 700 72 pp illus ----- and MCCmTY E C

]930 1111 GAltIlOUYDHAT( ~l1TAnOLIS~ OF lT1PA IULCHltA Hilgardia 5 61-100 iUu~

bull_- IWcl MALMSTIX 11 E 1926 GRAZ1XO ImUODS AXD FOItAGI llWDlCrOX ox Tilt XAl()XAL

PORE1TS r H Dtpt Jg-r Bull 1405 55 pp iIlUH SAltY1H T

1923 JoJ~gCTS O~ j)JIoFlml~Xl SH11~U A]) 1XrJlXS1IIEH ot GItAZIXG lION 1ll1l X11VI YEGETAT()X 1 1111 XOI~TII EltX OIUlAT PLAIXS JoUlLgt STATIOX r ti Dept Agr Bull J [70 40 pp ill us

ORGANIZATION O~ THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED

secretary of Agncultllre_____ ____ __ H~JNHY A YALLACE

Under Serreary _____ - _ _____ _____ bullbull _ _ _ ill L W lLSON

Assisiant Secretary_ - - _ bullbull _bullbull HAlmy L BHOWN

Director of Exlenl$ion Work___ bullbull C W WAHBUHTON

Director of Pinance _ bullbull ____ bull _ W A T UM 1

Director of lnforuwion __ _ _ _ _ _ _ M S ElSEXHOWEH

Direcor of Persoincl___ Y W STOCKllEHGEH

Director of Rescarch __ - IAMBS T TAnDfNEbull

solicitor ____ bull MASTIN C WHITE

Agricultural Adjustment Adminisirali07L 11 R TOILEY Administrator Bureau of Agricultural Econolllic~bullbull _ A C Bln(K Chief Bureau of Ag6cultllral HlgiTeering S H McCnony Chief Bureau of AnilIal Industry____ JOHN R MOHLEH Chicf Bureau of 13iologieell Survey___ _ InA N CABnUJLSON Chief Bureau of Chemistry and Soils_ HEXUY C KXlGHT Chief Commodity Exehangc Admimstr(lliel__ J T DUBL Chief Bureau of Dairy hduslru_ 0 K 1tJED Chief Bureau of Entomology and Plant Quarantinebullbull LEB A STHONO Chief Ofliee of Experiment SlationL__ _ JA~m8 T bullJAHJ)JNE Chief Parm Se(1lrity Administration_ w w Al~EXAXDEH Adminisralor Pood and Drug Administration___ VALmlt G CA~IIBELI Chief Porest Serticc ____ FEHDINMgtD A Sn(ox Cticf Burealt of Houw Econollics____ LOlIS] HTANIEY Chief Library _____ CIAltlllgL It ButNETT Librarian Burcellt of Plaut Ildll~lrl_ __ E C A l(jlI~l Chicf Bllreew of Public Hoad~__ T[(()~Ag H MACnONAID Chief 80il Conscrvalirli Serllice II JJ B lXXgTT Chief Weather Bureau _________ ___ bull WILLIS H GllEGG Chicf

This iJull(till isL tolltdhutioll from

POI(~t rnice ___ _ ioElWXAND A HIlAOX ChirJ

middotorc~t UC~(lr(h C L FOHSLING A~sist(lul Cdrf in Charfc

lJitijon of Ranac RI((Irrlt ___ R CHMlll[l Chicf Interlloutial7n POlrst a lUI Rongc ExshyREED HAll~r Director

periment Station

43

U S G(ERtjlpoundNf rRiNtiNG Ofnce 11H

1 The yenrly ealendnl of operations should be phtnlled so as to begin spring grazing after grasses reach 2-illeh height Orowth There is a minimum of yariation in this stage of development thus insuring available fornge in most yeurs and necessitating the maintenance of not more than a lO-clny supply of reserve feed for the exceptional year when fomge development is IILte This also precludes misuse of the range since from this time on forage groth will orditlllrily profess in advance of the sheep insUJing that ndequate feed will be available during the entire spring season if the range is not overshystocked Near Dubois Idaho 2-inch height growth is reached on the appro~-imate average date of April 22 Spring gmzing should end when bunchgrasses begin to cure which occms about Tllly 2 near Dubois

2 Full grf1zing should bei-gt111 wben summer runge is utilized but preferu bly nrter ruins sturt regrowth 01 grnsses or soften the cured bunchgrHsses Since fall grazing must end with the comillg of deep suow and this ocell1Ienee is extremel~T vmiable R 30-day reserve supply of feed or its equivalent 01 protected winter range over nnd aboe normal winter requirements should be lluulltailled as instuance against yenrs of enrly snows

3 For ranges hllwg a totnl plant (oyer of nbout 25 percent comshyprising approximately 45 per(ent of bunchgrnsses lInd palatable weeds and 55 percen t of sngeblush and 0 t her less pula til bIe shru bs stocking should be at the rute of two-thirds of a sheep pCI acre per month for approxinwtely 2Yz months in the spring nnd in the full A lower rnte of stocking is recommended where Jeluti-ely less bunchshygmss and weed fornge is nnliln ble tlnd a hig]1(r rute on Hrens supportshying a more dense stand of palatable vegetation

4 Rotation SPling gmzing is essentinl for mnintnining sagebrllshshybunchgrass rnnge under the couditions of (limate which preYnii in this section This systcm clln be npplied bT diyiding the mnge into two or more convenient uuits ilud routing the sbeep frOlll one to the other as the senson ndvnuces beginning this process with a different unit each succeeding yenr The periods of use and Tilte of sto(king should be ndj usted so tbn t nppro-illlut(ly one-third of the available bunchgrasses oyer the range ns n whok nre utilized during the spring season ufter grasses Teach 2-in(h height growth and not to exceed two-thirds of the total in the fall of aycrnge growth yeHrs This sysshytem of munugement willlIlsUle adequate forage in the poorest grOvth year and in good years will permit rnnge plants which mny hue been heasily grazed in prevJOus yeurs of drought to recover vigor ~[oreshyover because ample foruge is available under tbis system the sheep cau be expected to be maintained in a thrifty alld productive condition

5 Deferring nIl grnzing Ull til fall for a period of seycnd yeurs on successive portions of the range is recommended for obtaining maxishymum improvement of depleted range

42 TECJlNlUAL BIJLLErlN 600 U S DEPT Ol AGlUUIJLTUR1~

(1)

(2)

(3)

(4)

(51

(6)

(71

(fl)

(10i

LITERATURE CITED

COOPER r M Ilnd STOEHlt 1 A 1934 COMIAIUSOX OP ItAMBOUlLLIT COlmnDALE AXD COLUMBIA SHEEP

UXDJm lXTgRMOeXTAlX HAXla COXDITIONS l S Dept Agr Cire 308 16 pp ilIus

1OHSLIXO C L Ilnd STOUlII Eo V 1929 rlll CTIIIZATIOX OF IIllOSl JoOltAGI~ S HUMMlm RAXCH ]oOR

GAlTIm IX SOUTHWJSTERX U1AII t H Dept Agr Gire 62 30 pp ilIus

AHDlX] f 1 and ANDEHSON M 1919 HANGE MANAGIMEXT ON TUE NA 110 NAl FUHI~HIH C H Dept

A~r Bull 790 98 pp illus --- une FousrlxG G L

1922 RANGE AXD GATlLI~ MANAOIM IXT Dl1UQ DI(()tTUIIT U S Dept Agr Bull 103 84 ppbull LIlus

MeGA ftl E G 1937 Till lULATION (W GltoWIII 10 1111 AItYIN( (AHBlJIIYDltAT1 CUXshy

1gX~1 IN M()lNTAIX J11~OME GltASS l S Dept Agr Tech Bull 598 24 ]lp illus

NJoISON Eo 1934 rilE lXFLVEXCE 01 IUlClll1AlION AXD GltAUNG UPON BLACK

(tAMA OItASS HAXG1 L H DeJlt Agr Tech BuLl 409 32 pp illus

SAMIHOX A W 1918 CLllllAlI AXD l IA WI GIWWTll IN CEHlA1X VEGJTAIIVB ASSOCIAshy

TIONf LT H Dept A~r Bull 700 72 pp illus ----- and MCCmTY E C

]930 1111 GAltIlOUYDHAT( ~l1TAnOLIS~ OF lT1PA IULCHltA Hilgardia 5 61-100 iUu~

bull_- IWcl MALMSTIX 11 E 1926 GRAZ1XO ImUODS AXD FOItAGI llWDlCrOX ox Tilt XAl()XAL

PORE1TS r H Dtpt Jg-r Bull 1405 55 pp iIlUH SAltY1H T

1923 JoJ~gCTS O~ j)JIoFlml~Xl SH11~U A]) 1XrJlXS1IIEH ot GItAZIXG lION 1ll1l X11VI YEGETAT()X 1 1111 XOI~TII EltX OIUlAT PLAIXS JoUlLgt STATIOX r ti Dept Agr Bull J [70 40 pp ill us

ORGANIZATION O~ THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED

secretary of Agncultllre_____ ____ __ H~JNHY A YALLACE

Under Serreary _____ - _ _____ _____ bullbull _ _ _ ill L W lLSON

Assisiant Secretary_ - - _ bullbull _bullbull HAlmy L BHOWN

Director of Exlenl$ion Work___ bullbull C W WAHBUHTON

Director of Pinance _ bullbull ____ bull _ W A T UM 1

Director of lnforuwion __ _ _ _ _ _ _ M S ElSEXHOWEH

Direcor of Persoincl___ Y W STOCKllEHGEH

Director of Rescarch __ - IAMBS T TAnDfNEbull

solicitor ____ bull MASTIN C WHITE

Agricultural Adjustment Adminisirali07L 11 R TOILEY Administrator Bureau of Agricultural Econolllic~bullbull _ A C Bln(K Chief Bureau of Ag6cultllral HlgiTeering S H McCnony Chief Bureau of AnilIal Industry____ JOHN R MOHLEH Chicf Bureau of 13iologieell Survey___ _ InA N CABnUJLSON Chief Bureau of Chemistry and Soils_ HEXUY C KXlGHT Chief Commodity Exehangc Admimstr(lliel__ J T DUBL Chief Bureau of Dairy hduslru_ 0 K 1tJED Chief Bureau of Entomology and Plant Quarantinebullbull LEB A STHONO Chief Ofliee of Experiment SlationL__ _ JA~m8 T bullJAHJ)JNE Chief Parm Se(1lrity Administration_ w w Al~EXAXDEH Adminisralor Pood and Drug Administration___ VALmlt G CA~IIBELI Chief Porest Serticc ____ FEHDINMgtD A Sn(ox Cticf Burealt of Houw Econollics____ LOlIS] HTANIEY Chief Library _____ CIAltlllgL It ButNETT Librarian Burcellt of Plaut Ildll~lrl_ __ E C A l(jlI~l Chicf Bllreew of Public Hoad~__ T[(()~Ag H MACnONAID Chief 80il Conscrvalirli Serllice II JJ B lXXgTT Chief Weather Bureau _________ ___ bull WILLIS H GllEGG Chicf

This iJull(till isL tolltdhutioll from

POI(~t rnice ___ _ ioElWXAND A HIlAOX ChirJ

middotorc~t UC~(lr(h C L FOHSLING A~sist(lul Cdrf in Charfc

lJitijon of Ranac RI((Irrlt ___ R CHMlll[l Chicf Interlloutial7n POlrst a lUI Rongc ExshyREED HAll~r Director

periment Station

43

U S G(ERtjlpoundNf rRiNtiNG Ofnce 11H

42 TECJlNlUAL BIJLLErlN 600 U S DEPT Ol AGlUUIJLTUR1~

(1)

(2)

(3)

(4)

(51

(6)

(71

(fl)

(10i

LITERATURE CITED

COOPER r M Ilnd STOEHlt 1 A 1934 COMIAIUSOX OP ItAMBOUlLLIT COlmnDALE AXD COLUMBIA SHEEP

UXDJm lXTgRMOeXTAlX HAXla COXDITIONS l S Dept Agr Cire 308 16 pp ilIus

1OHSLIXO C L Ilnd STOUlII Eo V 1929 rlll CTIIIZATIOX OF IIllOSl JoOltAGI~ S HUMMlm RAXCH ]oOR

GAlTIm IX SOUTHWJSTERX U1AII t H Dept Agr Gire 62 30 pp ilIus

AHDlX] f 1 and ANDEHSON M 1919 HANGE MANAGIMEXT ON TUE NA 110 NAl FUHI~HIH C H Dept

A~r Bull 790 98 pp illus --- une FousrlxG G L

1922 RANGE AXD GATlLI~ MANAOIM IXT Dl1UQ DI(()tTUIIT U S Dept Agr Bull 103 84 ppbull LIlus

MeGA ftl E G 1937 Till lULATION (W GltoWIII 10 1111 AItYIN( (AHBlJIIYDltAT1 CUXshy

1gX~1 IN M()lNTAIX J11~OME GltASS l S Dept Agr Tech Bull 598 24 ]lp illus

NJoISON Eo 1934 rilE lXFLVEXCE 01 IUlClll1AlION AXD GltAUNG UPON BLACK

(tAMA OItASS HAXG1 L H DeJlt Agr Tech BuLl 409 32 pp illus

SAMIHOX A W 1918 CLllllAlI AXD l IA WI GIWWTll IN CEHlA1X VEGJTAIIVB ASSOCIAshy

TIONf LT H Dept A~r Bull 700 72 pp illus ----- and MCCmTY E C

]930 1111 GAltIlOUYDHAT( ~l1TAnOLIS~ OF lT1PA IULCHltA Hilgardia 5 61-100 iUu~

bull_- IWcl MALMSTIX 11 E 1926 GRAZ1XO ImUODS AXD FOItAGI llWDlCrOX ox Tilt XAl()XAL

PORE1TS r H Dtpt Jg-r Bull 1405 55 pp iIlUH SAltY1H T

1923 JoJ~gCTS O~ j)JIoFlml~Xl SH11~U A]) 1XrJlXS1IIEH ot GItAZIXG lION 1ll1l X11VI YEGETAT()X 1 1111 XOI~TII EltX OIUlAT PLAIXS JoUlLgt STATIOX r ti Dept Agr Bull J [70 40 pp ill us

ORGANIZATION O~ THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED

secretary of Agncultllre_____ ____ __ H~JNHY A YALLACE

Under Serreary _____ - _ _____ _____ bullbull _ _ _ ill L W lLSON

Assisiant Secretary_ - - _ bullbull _bullbull HAlmy L BHOWN

Director of Exlenl$ion Work___ bullbull C W WAHBUHTON

Director of Pinance _ bullbull ____ bull _ W A T UM 1

Director of lnforuwion __ _ _ _ _ _ _ M S ElSEXHOWEH

Direcor of Persoincl___ Y W STOCKllEHGEH

Director of Rescarch __ - IAMBS T TAnDfNEbull

solicitor ____ bull MASTIN C WHITE

Agricultural Adjustment Adminisirali07L 11 R TOILEY Administrator Bureau of Agricultural Econolllic~bullbull _ A C Bln(K Chief Bureau of Ag6cultllral HlgiTeering S H McCnony Chief Bureau of AnilIal Industry____ JOHN R MOHLEH Chicf Bureau of 13iologieell Survey___ _ InA N CABnUJLSON Chief Bureau of Chemistry and Soils_ HEXUY C KXlGHT Chief Commodity Exehangc Admimstr(lliel__ J T DUBL Chief Bureau of Dairy hduslru_ 0 K 1tJED Chief Bureau of Entomology and Plant Quarantinebullbull LEB A STHONO Chief Ofliee of Experiment SlationL__ _ JA~m8 T bullJAHJ)JNE Chief Parm Se(1lrity Administration_ w w Al~EXAXDEH Adminisralor Pood and Drug Administration___ VALmlt G CA~IIBELI Chief Porest Serticc ____ FEHDINMgtD A Sn(ox Cticf Burealt of Houw Econollics____ LOlIS] HTANIEY Chief Library _____ CIAltlllgL It ButNETT Librarian Burcellt of Plaut Ildll~lrl_ __ E C A l(jlI~l Chicf Bllreew of Public Hoad~__ T[(()~Ag H MACnONAID Chief 80il Conscrvalirli Serllice II JJ B lXXgTT Chief Weather Bureau _________ ___ bull WILLIS H GllEGG Chicf

This iJull(till isL tolltdhutioll from

POI(~t rnice ___ _ ioElWXAND A HIlAOX ChirJ

middotorc~t UC~(lr(h C L FOHSLING A~sist(lul Cdrf in Charfc

lJitijon of Ranac RI((Irrlt ___ R CHMlll[l Chicf Interlloutial7n POlrst a lUI Rongc ExshyREED HAll~r Director

periment Station

43

U S G(ERtjlpoundNf rRiNtiNG Ofnce 11H

ORGANIZATION O~ THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED

secretary of Agncultllre_____ ____ __ H~JNHY A YALLACE

Under Serreary _____ - _ _____ _____ bullbull _ _ _ ill L W lLSON

Assisiant Secretary_ - - _ bullbull _bullbull HAlmy L BHOWN

Director of Exlenl$ion Work___ bullbull C W WAHBUHTON

Director of Pinance _ bullbull ____ bull _ W A T UM 1

Director of lnforuwion __ _ _ _ _ _ _ M S ElSEXHOWEH

Direcor of Persoincl___ Y W STOCKllEHGEH

Director of Rescarch __ - IAMBS T TAnDfNEbull

solicitor ____ bull MASTIN C WHITE

Agricultural Adjustment Adminisirali07L 11 R TOILEY Administrator Bureau of Agricultural Econolllic~bullbull _ A C Bln(K Chief Bureau of Ag6cultllral HlgiTeering S H McCnony Chief Bureau of AnilIal Industry____ JOHN R MOHLEH Chicf Bureau of 13iologieell Survey___ _ InA N CABnUJLSON Chief Bureau of Chemistry and Soils_ HEXUY C KXlGHT Chief Commodity Exehangc Admimstr(lliel__ J T DUBL Chief Bureau of Dairy hduslru_ 0 K 1tJED Chief Bureau of Entomology and Plant Quarantinebullbull LEB A STHONO Chief Ofliee of Experiment SlationL__ _ JA~m8 T bullJAHJ)JNE Chief Parm Se(1lrity Administration_ w w Al~EXAXDEH Adminisralor Pood and Drug Administration___ VALmlt G CA~IIBELI Chief Porest Serticc ____ FEHDINMgtD A Sn(ox Cticf Burealt of Houw Econollics____ LOlIS] HTANIEY Chief Library _____ CIAltlllgL It ButNETT Librarian Burcellt of Plaut Ildll~lrl_ __ E C A l(jlI~l Chicf Bllreew of Public Hoad~__ T[(()~Ag H MACnONAID Chief 80il Conscrvalirli Serllice II JJ B lXXgTT Chief Weather Bureau _________ ___ bull WILLIS H GllEGG Chicf

This iJull(till isL tolltdhutioll from

POI(~t rnice ___ _ ioElWXAND A HIlAOX ChirJ

middotorc~t UC~(lr(h C L FOHSLING A~sist(lul Cdrf in Charfc

lJitijon of Ranac RI((Irrlt ___ R CHMlll[l Chicf Interlloutial7n POlrst a lUI Rongc ExshyREED HAll~r Director

periment Station

43

U S G(ERtjlpoundNf rRiNtiNG Ofnce 11H

1 t

_