what happened to 1966? - international plant nutrition ...webindex... · china s.s. portch, hong...

2001 Number 4

Potash & Phosphate InstituteSuite 110, 655 Engineering Drive

Norcross, Georgia 30092-2837

PeriodicalsPostage

I can’t believe it. Thirty-five years just flashed in front of my eyes. It couldn’t havebeen that long since Pat and the kids and I piled all our worldly possessions into a (small)U-Haul trailer hitched to our old Mercury and headed to Atlanta for my first real job. We wereuneasy about leaving Auburn University. We had set roots and established an extended fam-ily base among fellow graduate students during our nearly four years there. We were uncer-tain about the future.

Well, things have turned out just fine. As Pat and I make final preparations to leaveAtlanta...on our way to retirement, we count ourselves blessed for having had the opportuni-ty to spend 35 years in the fertilizer industry. My work has taken us from Auburn to Atlantato Albany, Georgia, to Stillwater, Oklahoma, and back to Atlanta. Along the way, we havebeen privileged to travel to such diverse places as China, Australia, and France...and hadthe opportunity to meet, work with, and become friends with some of the finest people in theworld.

One of the most difficult assignments in my career has been writing this pagein Better Crops with Plant Food for the past couple of years. I’m humbled becausethere could never be another who frames his or her words in a more eloquent manner thandid the late Dr. J. Fielding Reed, former PPI President. Between 1983 and 1999 he ownedthis space. Yet, it’s a special honor for me to share the podium with Fielding.

This will be my last column as Executive Vice President of the Institute.However, Dr. David Dibb, PPI President, has asked me to continue with the page, so I hopeyou will visit me here for a while longer. In the meantime, I wish to express my appreciationto all my co-workers at PPI past and present. They have been the biggest reason...along withfolks like Lance Murrell, Don Ball, Billy Darnell, Bob Westerman, and scores of other col-leagues...that my job has been the best there is.

Pat says for me to not go around inviting everybody to come and see us at Amelia Island,Florida. I won’t do that, but if you’re ever in the area...

What Happened to 1966?

IN THIS ISSUE

• Soybean Responseto ResidualPhosphorus forVarious Placementsand TillagePractices

• Soil PhosphorusMay Be Importantto Beef HerdHealth andPerformance

• Predicting AnnualPhosphorus Lossesfrom Fields Usingthe P Index forPasturesand much more...

Our Cover: Aerial view of corn harvest near Davenport, Iowa.Photo Credit: Charles McDowell from Grant Heilman Photography, Inc.

Editor: Donald L. ArmstrongAssistant Editor: Katherine P. Griffin Circulation Manager: Carol MeesDesign: Debbie Nguyen, S.O.H.O.

Potash & Phosphate Institute (PPI) C.S. Hoffman, Chairman of the Board

IMC Global Inc.H. Mathot, Vice Chairman of the Board

Cargill, Incorporated

HEADQUARTERS: NORCROSS, GEORGIA, U.S.A.D.W. Dibb, President B.C. Darst, Executive Vice President T.L. Roberts, Vice President, PPIC, Latin AmericaC.V. Holcomb, Assistant Treasurer S.O. Danner, Executive Assistant W.R. Agerton, Communications SpecialistS.J. Couch, Information Management SpecialistB. Rose, Statistics/AccountingC. Heaton, Circulation Assistant

NORTH AMERICAN PROGRAMS-Brookings, South DakotaP.E. Fixen, Senior Vice PresidentP. Pates, Secretary

REGIONAL DIRECTORS-North America T.W. Bruulsema, Guelph, OntarioA.M. Johnston, Saskatoon, SaskatchewanA.E. Ludwick, Bodega Bay, California T.S. Murrell, Woodbury, MinnesotaH.F. Reetz, Jr., Monticello, Illinois C.S. Snyder, Conway, Arkansas W.M. Stewart, Lubbock, TexasN.R. Usherwood, Norcross, Georgia

INTERNATIONAL PROGRAMS-Saskatoon, SaskatchewanM.D. Stauffer, Senior Vice President, International

Programs (PPI), and President, Potash & Phosphate Institute of Canada (PPIC)

G. Sulewski, AgronomistL.M. Doell, Administrative AssistantD. Gibson, Executive SecretaryK. Segi, Receptionist

INTERNATIONAL PROGRAM LOCATIONS Brazil T. Yamada, Piracicaba, POTAFOSChina S.S. Portch, Hong Kong

J. Wang, Saskatoon, Saskatchewan Ji-yun Jin, Beijing Fang Chen, WuhanShihua Tu, ChengduRonggui Wu, BeijingRongle Liu, Beijing

India K.N. Tiwari, Gurgaon, Haryana T.N. Rao, Secunderabad, Andhra PradeshK. Majumdar, Calcutta

Northern Latin America J. Espinosa, Quito, Ecuador, INPOFOSLatin America-Southern Cone F.O. Garcia, Buenos Aires, INPOFOS Mexico I. Lazcano-Ferrat, Querétaro, INPOFOSEast and Southeast Asia E. Mutert, Singapore

T.H. Fairhurst, Singapore

BETTER CROPS WITH PLANT FOOD(ISSN:0006-0089) is published quarterly by the Potash & PhosphateInstitute (PPI). Periodicals postage paid at Norcross, GA, and at additional mailing offices (USPS 012-713). Subscription free on request to qualified individuals; others $8.00 per year or $2.00 perissue. POSTMASTER: Send address changes to Better Crops with PlantFood, 655 Engineering Drive, Suite 110, Norcross, GA 30092-2837.Phone (770) 447-0335; fax (770) 448-0439. www.ppi-ppic.org. Copyright 2001 by Potash & Phosphate Institute.

Members: Agrium Inc. • Cargill, Incorporated • CF Industries, Inc. • Farmland Hydro, Inc. • IMC Global Inc.Intrepid Mining, LLC/Moab Potash • Mississippi Chemical Corporation • Potash Corporation of Saskatchewan Inc. • Simplot

Contact PPI/PPIC/FAR on the Internet 3

Correction to Data in 3Better Crops #3, 2001

Soil Phosphorus May Be Important to 4Beef Herd Health and Performance(Missouri)

Ryan Lock, Robert Kallenbach, Dale Blevins, Tim Reinbott, Greg Bishop-Hurley, Richard Crawford, Jr., and Matt Massie

The Magruder Plots – Long-Term 6Wheat Fertility Research (Oklahoma)

R.W. Mullen, K.W. Freeman, G.V. Johnson, and W.R. Raun

Onion Response to Phosphorus Placement 9as Affected by Fumigation (Idaho)

Brad Brown

InfoAg 2001 Rates High Marks 11from Participants

Soybean Response to Residual 12Phosphorus for Various Placementsand Tillage Practices (Minnesota)

G.W. Randall, J.A. Vetsch, andT.S. Murrell

Research Notes: No-Tillage Soybean 15Response to Banded and Broadcast andDirect and Residual Fertilizer Phosphorus and Potassium Applications (Iowa)

Predicting Annual Phosphorus Losses 16from Fields Using the Phosphorus Indexfor Pastures (Arkansas)

P.B. DeLaune and P.A. Moore, Jr.

Spring Wheat Cultivar Response to 20Potassium Chloride Fertilization(Manitoba)

Cynthia A. Grant, Debra L. McLaren,and Adrian M. Johnston

What Happened to 1966? 24B.C. Darst

C O N T E N T S

Vol. LXXXV (85) 2001, No. 4

Acalculation error oc-curred in Table 2 ofthe article titled

“Nutrient Management inMixed Forage Systems”, whichappeared on pages 16 and 17in Better Crops with PlantFood, No. 3, 2001. The cor-rected Table 2 is shown here.While the values as shown ear-lier were not correct, the state-ments and conclusions in theoriginal text remain valid.

Better Crops/Vol. 85 (2001, No. 4) 3

Contact PPI/PPIC/FAR on the Internet

You can reach the Potash &Phosphate Institute (PPI), Potash &Phosphate Institute of Canada

(PPIC), and the Foundation for AgronomicResearch (FAR) on-line. To visit the PPI/PPIC website use www.ppi-ppic.org or usewww.ppi-far.org to go to the FAR website.

Both quantity and quality of informa-tion now available in electronic form con-tinue to increase at PPI/PPIC/FAR. There

are frequent additions and improvements tothe sites, which are searchable. Current andprevious issues of Better Crops with PlantFood, Better Crops International, and otherpublications are available as pdf files.

Each of the regions of North Americaand globally where the Institute has agro-nomic research and education programsnow has an individualized website accessi-ble from the central site.

Nutrient Nutrient balance1, lb/A Final soil test2, lb/Atreatment P2O5 K2O P K

Control -217 -543 10 92N fertilizer -264 -622 9 88NPK fertilizer 184 -16 13 116LD manure 209 84 12 1241Sum of nutrients applied in fertilizer and manure minus thoseremoved in forage harvest.2Modified Morgan soil test level in 2000. Initial soil test levels in1995 were 15 lb/A for P and 134 lb/A for K.

TABLE 2. Nutrient balance over the six years and final soil test levels.

Correction to Data in Better Crops #3, 2001

Grass tetany is a nutritional disease ofruminants and has been associatedwith low levels of Mg in forage. This

disorder most often affects lactating cowsgrazing lush, cool-season grass pastures. It ismost common during early spring when thegrass has a seasonally lowMg concentration and whenspring-calving cows have athree-fold greater demand forMg as a result of milk pro-duction.

Although the diseasecan prove fatal, it rarely pro-gresses to clinical symptoms.More often, a cow suffersfrom hypomagnesemia, orsub-clinical grass tetany.Hypomagnesemia is a pre-cursor to grass tetany, with symptoms that are difficult to detect, includingdecreased feed intake, lowered milk pro-duction, and loss of body condition. Itaffects cow performance and health anddecreases gains of suckling calves. Thus,it is important that cows consume ade-quate Mg to ensure the performance ofthe herd is not compromised.

Typically, producers offer cattle amineral supplement rich in Mg duringthe grass tetany season. However, thereare problems associated with mineralsupplementation. These include the cost,palatability, reliability, and potency ofthe supplements. Given the fact that sup-plements can be expensive and do notalways work, interest has grown toincrease the Mg in cool-season grasses.With this method, a cow would receive

her daily requirement of Mg while grazing.Recent work at the University of

Missouri indicates that maintaining soil test Pat greater than 30 lb/A can increase the Mgconcentration of cool season grasses duringspring. Reinbott and Blevins in Missouri pub-

lished reports in 1991, 1994and 1997, consistently show-ing that plants fertilized withP in spring have greater Mgconcentrations compared tothose grown on low P soils.

Materials and MethodsIn a continuation of the

work by Reinbott andBlevins, a grazing experi-ment was conducted at theSouthwest Research and

4 Better Crops/Vol. 85 (2001, No. 4)

Soil Phosphorus May Be Important toBeef Herd Health and PerformanceB y R y a n L o c k , R o b e r t K a l l e n b a c h , D a l e B l e v i n s , T i m R e i n b o t t , G r e g B i s h o p - H u r l e y, R i c h a r d C r a w f o r d , J r . , a n d M a t t M a s s i e

M I S S O U R I

Recent research results inMissouri agree with earlierfindings that soil phosphorus(P) is important in boostingmagnesium (Mg) uptake by tall fescue. Phosphorus fertilization of pastures is a good alternative to Mg supplements for protectingagainst grass tetany and canhelp increase calf gains.

Missouri research indicates that P fertilization of tall fes-cue pastures can increase forage Mg levels and helpprotect against grass tetany. Pasture on right in photo,fertilized with P, had a soil test of 30 lb/A Bray P-1.Unfertilized pasture at left had a soil test of only 5 lb/A.


Education Center near Mt. Vernon during thespring of 2000 and 2001. The first objectivewas to determine if P fertilization of tall fes-cue would increase the Mg levels in the grassas well as in the animals grazing the grass.Another objective was to compare the Mg sta-tus of cows grazing P-fertilized tall fescue tothose receiving Mg supplement. The experi-mental design was a randomized completeblock with three treatments and three replica-tions. There were nine pastures, and threecows grazed in each pasture for 56 daysbeginning February 15, 2000 and againMarch 6, 2001. The treatments were:1) Cows grazed tall fescue grown on soil

with 34 lb/A available P;2) Cows grazed tall fescue grown on soil

with 6 lb/A available P while supple-mented with 12 percent Mg mineralblocks free choice;

3) Cows grazed tall fescue grown on soilwith 6 lb/A available P with no supple-mentation.For simplicity, the treatments will be

referred to as P fertilized, Mg supplement,and control, respectively.

Blood samples were taken from the cows,and forage samples were harvested on the firstday of the trial and at 14-day intervals. TheMg concentration of the samples was ana-lyzed. Cows and calves were weighed at thesetimes. Forage availability was kept equalamong pastures using electric fencing to con-trol grazing. This method ensured that the Mgstatus of the animals was a function of foragequality rather than quantity consumed.

Results and DiscussionForage Mg levels. Preliminary results

from this grazing experiment indicate that Pfertilization of tall fescue pasture increasedthe forage Mg levels nearly 20 percent com-pared to pastures not fertilized with P. Thiswas the case in both years and agrees withprevious work suggesting that soil P regulatesMg uptake by tall fescue.

Blood serum Mg levels. Except forMarch 20, 2001, cows grazing P fertilized pas-tures and cows receiving Mg supplementshowed equal blood serum Mg levels on allsampling dates. On the mentioned date, cows

in the P fertilized pastures showed nearly 33percent less Mg in blood serum than cowsreceiving Mg supplement. Cold temperaturesand snowfall during the three days before thissampling likely reduced the forage intake ofthese animals because control animals alsoshowed decreased Mg levels at this time,although not as severe. These data suggestthat the two groups depending on forage asthe only source for Mg could not consumeenough dry matter due to the weather condi-tions at that time. As a result of theirdecreased forage intake, the cows wereunable to consume their daily Mg require-ment, and blood serum Mg levels dropped.Cows supplemented with Mg were able toconsume the supplement, and their bloodserum levels did not drop. As the weatherbecame milder, the cows’ Mg status in the Pfertilized and control groups returned to pre-vious levels.

The decrease in blood serum Mg of cowsgrazing P fertilized pasture compared to cowsin the control or Mg supplement groups mayhave also been due to greater milk productioncoupled with the weather conditions. Duringcold weather, average daily gains (ADG) of suckling calves were 30 percent higherwhen their mothers grazed P fertilized tallfescue compared to cows grazing pastures notfertilized with P. This higher rate of gain incalves is perhaps a result of greater milk pro-duction by the cows. Since Mg is importantfor milk production, cows in P fertilized tallfescue may have had more demand for Mg toproduce the larger volume of milk needed forthe increased calf gains. Therefore, harsh

(continued on page 8)

Mother cow management SucklingPasture calf

Bray P-1, Mg ADG,Treatment lb/A supplement lb

P fertilized 34 Yes 2.44Mg supplement 6 Yes 2.23Control 6 No 2.16

LSD (0.05) 0.18

TABLE 1. Average daily gain of suckling calves for 56 days during the springseasons of 2000 and 2001.

In 1891, A.C. Magruder established a con-tinuous winter wheat fertility study atOklahoma State University that remains

ongoing today. The experiment was initiallyestablished to evaluate the effect of manureapplication on wheat yield and determinehow long the soil could sus-tain continuous wheat pro-duction. In 1930, treatmentsevaluating inorganic sourcesof N, P and K were added.The data set collected overthe last 110 years has been avaluable source of informa-tion for long-term monocul-ture wheat fertility and sus-tainable agriculture.

During the early decadesof the trial, manure application resulted in a

marked increase in yield when compared tothe unfertilized check plot (Figure 1). Eventhen, the realization that there was not enoughmanure to cover all of Oklahoma’s wheatground was noted. As the ability to synthesizeinorganic fertilizers increased, treatments

evaluating inorganic forms ofN, P and K were added to thetrial. From the time inorgan-ic fertilizers were first added(1929), yields due to thesematerials have matched orexceeded those of the man-ure treatment.

Another important aspectof the Magruder Plots isidentifying the onset ofmacronutrient deficiencies.

Comparison of the P only and the NP treat-


The Magruder Plots – Long-Term Wheat Fertility ResearchB y R . W. M u l l e n , K . W. F r e e m a n , G . V. J o h n s o n , a n d W. R . R a u n

O K L A H O M A

This 110-year-old wheatfertility study is a convinc-ing example of the impor-tance of recognizing a soil’snutrient supplying capabili-ty in nutrient management.Phosphorus (P) was thefirst limiting nutrient, thennitrogen (N), and finallypotassium (K).

Figure 1. Ten-year average yields for the Magruder Plot treatments, Stillwater, OK, 1890 to 2000.Manure: 1891-1967, applied at a rate of 120 lb N/A every four years; 1968-present, applied at a rate of 240 lb N/A every four yearsCheck: no soil amendments addedP: 1930-1967, P applied as ordinary superphosphate at a rate of 30 lb P2O5; 1968-present, applied as triple superphosphateNP: 1930-1945, N applied as sodium nitrate at a rate of 33 lb N/A; 1946-1967, N applied as ammonium nitrate at a rate of 33 lb N/A;

1968-present, N applied as ammonium nitrate at a rate of 60 lb N/A; P application same as P only treatmentNPK: N and P treatment same as NP treatment; 1930-present, K applied as potassium chloride at a rate of 30 lb K2O/ANPKL: N, P and K applied the same as NPK treatment; lime (L) applied when soil pH < 5.5

05

1015202530354045

Manure Check P NP NPK NPKL

1891-1899

1900-1909

1910-1919

1920-1929

1930-1939

1940-1949

1950-1959

1960-1969

1970-1979

1980-1989

1990-1999

2000-2001

Time, 10-year intervals

Yiel

d, b

u/A

ments shows that a considerable difference inyield due to N fertilization was not noted untilthe 1960s (Figure 2). Thus, early in thestudy, N in rainfall and that mineralized fromsoil organic matter were sufficient to meetplant needs at these dryland yield levels. Aresponse to applied K was not observed untilthe 1980s when the yield of the NPK fertil-ized plots minus that of the NP fertilized plotsbegan to show a difference (Figure 2). Thiscoincides with the disappearance of a Presponse in the P only treatment resulting pri-marily from the development of N deficiency.However, K was likely a contributing factorsince it was also becoming yield limiting. It isinteresting to note that when N, P, K, and limeare adequately supplied, there has been little

if any benefit from the addition of secondaryand micronutrients supplied by the manuretreatment.

Soil N has decreased notably over thelast 100 years, as has the soil organic matterlevel. In 1893, N and organic matter in thesurface soil were 0.16 and 3.58 percent,respectively. After 108 years of monoculture,winter wheat under conventional tillage, soilN and organic matter levels have droppedbelow 0.06 and 1.50 percent, respectively(Figures 3 and 4). The decrease is mostnotable in the 0 N treatments, resulting fromdepletion of native N for crop needs. Soil P


Figure 2. Differences among selected treatments of the Magruder Plots, 1930-2000.

NP-P: difference in winter wheat yield between NP treatment and P only treatment

P-Check: difference in winter wheat yield between P onlytreatment and check

NPK-NP: difference in winter wheat yield between NPKtreatment and NP treatment

02468

101214161820 NP-P P-Check NPK-NP

1931-1940

1941-1950

1951-1960

1961-1970

1971-1980

1981-1990

1991-2000

Time, 10-year intervals

Diff

eren

ce in

yie

ld, b

u/A

Figure 3. Change in soil organic matter over the last 100 years of the Magruder Plots.

0

1

2

3

4

Manure Check

1880 1900 1920 1940 1960 1980 2000Year

Org

anic

mat

ter,

%

2020

Figure 4. Change in total soil N over the last 100 years of the Magruder Plots.

0.00

0.05

0.10

0.15

0.20

Manure Check

Year

Tota

l N, %

19201880 1900 1940 1960 1980 2000 2020

Dr. Bill Webb, Dr. Robert Westerman, and Dr. BillyTucker (left to right) each served as Manager ofthe Magruder Plots in past years. Dr. W.R. Raunhas handled the responsibility since 1992.

P Kparts per million (ppm)

Treatment 19671

Check 17.7 316Manure 27.3 371P only 50.6 259NP 35.2 311NPK 37.5 383NPKL 30.6 350

19971

Check 6.7 231Manure 41.3 230P only 55.7 219NP 46.3 257NPK 43.2 282NPKL 38.3 2621In 1967, Bray-Kurtz P-1 for P and ammoniumacetate for K; in 1997, both P and K by Mehlich 3.

TABLE 1. Soil P and K levels measured in 1967 and 1997.

and K levels have changed considerably overthe last 34 years (Table 1). Soil test P hasdecreased in the check, and P levels of the Ponly treatment are higher than other treat-ments because N has been limiting, thusreducing yields and P removal.

The data collected from 110 years ofmonoculture winter wheat on the MagruderPlots have been invaluable. Identifying that inthe 1980s soil K was depleted to levels whereyield was adversely affected emphasizes theneed for soil testing and proper nutrient man-agement. The lack of a considerable responseto inorganic N fertilization prior to the 1960salso illustrates that the original source of N inthe soil is organic matter. Its contribution of Nvia mineralization was and continues to bequite significant. On these prairie soils, firsttilled in 1892 and in continuous winter wheatsince, it took 70 and 90 years to observe N andK responses, respectively.


The authors are researchers at Oklahoma State University, Stillwater.

weather conditions and a greater demandfor Mg may be the cause for the decrease inblood serum Mg observed on March 20,2001.

Calf performance. Calves had high-er rates of gain in both years when theirmothers grazed tall fescue fertilized with P(Table 1). We thought that milk qualitymight have been affected by P fertilization.However, when milk samples were ana-lyzed for protein, no differences were foundamong treatments. Therefore, it seems thatthe volume of milk produced may havebeen greater for the P fertilized group com-pared to the Mg supplement and controlanimals. As a result, the calves grew faster.If forage availability is greater, cows canproduce more milk for their calves.However, we attempted to keep the amountof available forage equal among pastures.Therefore, the greater milk production mayhave been the result of increased foragequality, although we do not have those dataat this time.

SummaryThese results agree with previous

research indicating the importance of soil Pin increasing Mg uptake by tall fescue.Fertilizing pastures with P compares favor-ably to use of Mg supplements to protectagainst grass tetany. Further, P fertilizationprovides additional benefits to cattlemen,including greater calf gains.

Mr. Lock is Graduate Research Assistant, Dr.Kallenbach is Assistant Professor and ExtensionForage Crops Specialist, Dr. Blevins is Professor,Mr. Reinbott is Research Associate, and Dr.Bishop-Hurley is Post-Doctoral Fellow, all withDepartment of Agronomy, University of Missouri,Columbia. Dr. Crawford is Research AssistantProfessor and Mr. Massie is Senior ResearchSpecialist, both at Southwest Missouri Researchand Education Center, Mt. Vernon.

Beef Herd Health...(continued from page 5)

Unrestricted early season growth isessential for maximizing onion yieldsand financial returns. The fumigant

Metam Sodium (Vapam®) is commonly usedas a non-selective biocide for controlling soilborne diseases, insects, nematodes, and weedsfor Idaho’s Treasure Valleyonions. But it can stunt earlyseason growth, especially inhigh lime soils. The stuntingis commonly attributed to lossof beneficial soil fungi calledmycorrhizae that help onionsaccess certain immobile soilnutrients such as P.

Mycorrhizal filamentsextend from infected rootsand essentially serve as rootextensions, allowing theonions to explore greater soilvolumes. Onions in high limesoils are particularly suscep-tible to stunting with Vapam®because available soil P isreduced with lime, and myc-orrhizae in the fumigated soilare not available to compensate.

Previous research by the University ofIdaho indicated that fall broadcast P reducedor altogether prevented onion stunting in highlime soils fall fumigated with Vapam®. The Prequirements of onions were clearly increasedwhen fumigant was used. Broadcast P fertiliz-ers followed by fall bedding is a common prac-tice for this production area.

Banding P for onions has been more effec-tive than broadcasting P in the Midwest, butnot always in other onion production regions.Such evaluations had not been conducted in

the Treasure Valley. Our research objectivewas to further evaluate the stunting effects ofVapam® in relation to applied P, to comparebroadcast vs. banded P for the area’s produc-tion system, and to determine whether fumiga-tion affected soil P availability for subsequent

wheat crops.The study was conducted

for three years at theUniversity of Idaho ParmaResearch and ExtensionCenter on a Nyssaton siltloam soil with low to moderateavailable P [6.8 to 8.2 partsper million (ppm) sodiumbicarbonate P] and apprecia-ble free lime (11 to 12 per-cent). Phosphorus rates (0 or58 lb P2O5/A) as triple super-phosphate were either fallbroadcast or fall banded inbed centers. All P treatmentswere evaluated with and with-out Vapam® (33 percentactive ingredient) injected at35 gal/A after beds were

formed in the fall. The treatments were evalu-ated with six replications. Onions followed aprevious wheat crop.

Yellow Sweet Spanish onion double rows(4 in. apart) were planted on the 22-in. beds inearly spring to straddle the banded P. Nitrogen(N) was sidedressed as urea prior to bulbingaccording to University of Idaho fertilizerguide recommendations. The onions were fur-row-irrigated as needed. Weeds and thripswere controlled with labeled pesticides.

Fall fumigation consistently stunted earlyseason onion growth (June dry weight) if no P


Onion Response to Phosphorus Placementas Affected by FumigationB y B r a d B r o w n

Crops such as onions whichdepend on mycorrhizae fungiare especially vulnerable tomarginal phosphorus (P)conditions in fumigated soils.Experience in the TreasureValley of Idaho has shownthat fumigation of high limesoils can stunt early seasononion growth, but P can fullycompensate in some cases.Our research showed thatbroadcast fertilizer P prior tobedding was more effectivefor supporting early seasongrowth than P banded belowand to the side of plantedonion seed.

I D A H O


was fall applied or if the P was fall banded(Figure 1). Broadcast P in two of three yearswas the only P application that fully compen-sated for the fumigant-induced stunting ofearly season growth. Where Vapam® was uti-lized, banded P was clearly less effective thanbroadcast P.

The importance of mycorrhizae in thestunting of onions could not be determined inthis study. Whereas the stunting effects offumigation in one year were associated withgreatly reduced mycorrhizal colonization, myc-orrhizal colonization was uniformly low inother years and not influenced by fumigant,although stunting of the onions was just assevere.

Fumigation did not affect the uptake ofpotassium (K), calcium (Ca), magnesium (Mg),and sulfur (S) in any year. But it did reduce theuptake of zinc (Zn), manganese (Mn), iron (Fe),and copper (Cu) in 1999, and the concentra-tions and uptake averaged lower in 2000. Thedifferences were not statistically significant(data not shown). Fumigant-induced micronu-trient shortages, therefore, may contribute toonion stunting in some years in the TreasureValley.

The uptake of P by onions in June was notaffected by fall-applied P, unless the soil hadbeen fumigated. When fumigated, June Puptake and tissue P concentrations generally

increased with added P, especially broadcast P.The results confirm that early season onionrequirements for fertilizer P are higher forfumigated soils.

Onion yields were limited by P deficiencyin only one year without fumigation, but werelimited in two of three years with fumigation.

Fumigation consistently delayed maturityregardless of fall-applied P, ultimately re-ducing bulb size and yield at harvest. Amongthe fumigated treatments, yield of small bulbsusually tended to be greater with fumigationand banded P, (Figure 2) whereas yield of large bulbs or colossals was greater with

Figure 1. Early season onion growth as affected by P treatment and year. Parma, 1998-00. Different letter denotes a statistical difference between non-fumigated and fumigated treatments at p < 0.05 within a given year.

0.0

0.1

0.2

0.3

0.4

0.5

Non

e

Broa

dcas

t

Band

ed

Non

e

Broa

dcas

t

Band

ed

Non

e

Broa

dcas

t

Band

ed

a

c

a

b b

bb

bb

a

aa

aa

P treatment

June

dry

wei

ght,

tons

/A

Non-fumigatedFumigated

1998

1999

2000

Figure 2. Small onion yield as affected by P treat-ment. Parma, 1998-00. Different letter denotes a statistical difference between non-fumigated and fumigated treat-ments at p < 0.05 within a given year.

0

100

200

300

400

Non

e

Broa

dcas

t

Band

ed

Non

e

Broa

dcas

t

Band

ed

Non

e

Broa

dcas

t

Band

ed

ab

b b b

bb

a

aa

aa

P treatment

Smal

l yie

ld, c

wt/A Non-fumigated

Fumigated

1998 1999

2000

Onion stunting in the foreground resulted with fallfumigation without P. Onions in the backgroundwere non-fumigated, with P. At far right, onionswere non-fumigated, without P.

fumigation and broadcast P (Figure 3). Butfall-applied P fully compensated for the effectsof fumigation on bulb size and yield in two ofthree years if P was broadcast and one of thethree years if it was banded. Additional avail-able P was required for fumigated soil to matchyields from soils not fumigated. Whereas onionyield did not differ for broadcast and banded Pin two years, yield was lower with banding inone year.

The effects of fumigation on subsequentcrops have not been widely reported. Winterwheat was fall planted after the onions to mea-sure residual effects from the previous year Pfertilizer and fumigation treatments. Theadverse effects of fumigation on available soilP extended into the following wheat crop inboth of the seasons for which data are avail-able. Either P uptake by wheat at heading orgrain yield at maturity was reduced the yearfollowing onions grown on fumigated soils.However, wheat grain yield and P uptake werenot affected by fumigation the previous year ifP had been applied to the onions.

SummaryFumigation-induced stunting of onions

prior to bulbing was striking and consistenteach year in this high lime soil, and fall-applied P could not fully compensate for theeffect in all years. Other factors appear to beinvolved which this study was not designed toevaluate. Banded P with soil-injected Vapam®was less effective than broadcast P. There arecompelling pest control reasons to fumigateonion production fields in the Treasure Valley,

but adequate levels of P, and possibly othernutrients, are essential to avoid reduced yieldsof both onions and subsequent wheat in highlime soils.

The author (e-mail: [email protected].) is anExtension Soil and Crop Management Specialist atthe University of Idaho, Parma Research andExtension Center, 29603 U of I Lane, Parma, Idaho83660. Phone (208) 722-6701 ext. 216; fax (208)722-6708.

This research was supported by the Idaho-EasternOregon Onion Growers Association.


Figure 3. Colossal onion yield as affected by P treatment and year. Parma, 1998-00. Different letter denotes a statistical difference between non-fumigated and fumigated treatments at p < 0.05 within agiven year.

0

100

200

300

400

Non

e

Broa

dcas

t

Band

ed

Non

e

Broa

dcas

t

Band

ed

Non

e

Broa

dcas

t

Band

ed

a

b

b

b

b

b

a

a

aa

P treatment

Colo

ssal

yie

ld, c

wt/A

Non-fumigatedFumigated

1998

1999

2000

The fifth in the series of Information AgricultureConferences, InfoAg 2001, took place in August atIndianapolis, Indiana. More than 400 attended the

event, which was organized by PPI/PPIC/FAR in coopera-tion with other partners, sponsors and supporters. Programpartners for InfoAg 2001 included CyberDealer and CropLifemagazines (Meister Publishing) and Indiana PrairieFarmer/Prairie Farmer magazines (Farm ProgressCompanies).

For more information, call (605) 692-6280 or fax (605) 697-7149. Proceedings papersfor InfoAg 2001 are posted on the website at www.ppi-far.org/infoag.

InfoAg 2001 Rates High Marks from Participants

When soil tests are low, substantial soybean yieldincreases may result from residual P applied eitherbroadcast or in bands the previous year for corn.

Strip tillage, or zone tillage, disturbs the soilto a depth of 7 to 8 in. and creates a 4 to 6in. wide by 1 to 2 in. high mound of soil thatis free of residue. The tilled area is warmerand drier at planting time. One-pass sec-ondary tillage systems consist of no primary

Row-crop agriculture in the Missis-sippi River Basin is under intensepressure to reduce sediment and

nutrient losses by practicing less tillage andmore precise application and placement ofnutrients, especially nitrogen (N) and P. Bykeeping more crop residueat the soil surface, reducedtillage systems can limitsediment losses. The tillagesystem keeping the mostresidue at the surface is no-till. However, in the north-ern portions of the CornBelt, corn yields are gener-ally lower in no-till systemsbecause of wetter and coolersoils at the time of planting.Other tillage systems arebeing investigated to find solutions offeringadequate surface cover while providing goodgrowing conditions. Currently used conser-vation tillage alternatives are strip tillage(strip-till) and one-pass secondary tillage.


Soybean Response to ResidualPhosphorus for Various Placements andTillage PracticesB y G . W. R a n d a l l , J . A . Ve t s c h , a n d T. S . M u r r e l l

M I N N E S O T A

tillage in the fall and eitherfield cultivation or a diskingoperation in the spring.

In the corn growingareas of Minnesota, soy-beans frequently follow cornin crop rotations. The effectsof surface residue on tem-perature and moisture arenot considered as importantfor soybeans, which can beplanted later when soils aredrier and warmer. Therefore,

strip-till is not normally performed for thesoybean crop. Instead, where strip-till wasused in the previous corn year, most produc-ers revert to no-till for the subsequent soy-bean crop.

Most producers do not apply fertilizerprior to planting soybeans. They generallyrely on the residual effects of fertilizer, pri-marily P and potassium (K), applied for the

Under very low soil testphosphorus (P) levels, significant soybean yieldresponses to residual Pwere observed for allplacements in a Minnesotastudy. Banded applicationsat half the recommendedbroadcast rate were notsufficient to optimize soy-bean yields.

Soybean yield, bu/ATillage High P site Low P site

No-till 53.4 41.5One-pass 55.6 42.5Strip-till (c); no-till (s) 53.7 43.5Chisel 56.1 42.1

TABLE 1. Soybean yields associated with each tillage practice, averaged across years (1998-2000) and similar P management practices.

prior corn crop. Previous research inMinnesota has shown that under convention-al tillage, soybeans generally respond best tobroadcast applications of P. However, inreduced tillage systems, less soil distur-bance limits the opportunity for incorpora-tion of broadcast P fertilizers. Therefore,banded applications, as with starters or deepbanding, serve as viable alternatives tobroadcast applications and are commonlyused for corn. Application of P below thesoil as bands serves two purposes: 1) Itplaces P in the soil volume where it is easi-ly accessible by roots and 2) concentratedzones of P can decrease fixation, making Pmore readily available for plant uptake. Forthese reasons, the University of Minnesotarecommends that rates of banded P bereduced to half the recommended broadcastrate at Bray P-1 greater than 5 parts per mil-lion (ppm). We tested this recommendationto understand how P management for cornaffected soybean response in the subsequentgrowing season.

A study was begun in the fall of 1996 ona tile-drained Nicollet-Webster clay loamsoil complex located at the SouthernResearch and Outreach Center, Waseca,Minnesota. The study utilized a corn-soy-bean rotation and several P and tillage man-agement practices. Two adjacent sites wereused. The high P site had been previouslymaintained at approximately 19 ppm BrayP-1 with periodicP fertilizer appli-cations while in acorn-corn-corn-soybean rotation.The low P site hadpreviously been ina continuous cornrotation andreceived no P for15 years to minesoil P to very lowlevels (3 to 4 ppmBray P-1). Tillagepractices were no-till for both cornand soybean years,one pass of a field

cultivator (for corn) or a disk (for soybeans)in the spring (one-pass), fall strip-till forcorn [strip till (c)], followed by no-till forsoybeans [no-till (s)], and chisel tillage(chisel) utilizing a chisel in the fall plus afield cultivator in the spring for both crops.

Phosphorus was applied only for corn.Phosphorus application methods for alltillage practices in the corn year included acheck (no P) and a band application in theseed furrow at planting (starter). Broadcastapplications with subsequent incorporationwere made for the one-pass and chisel sys-tems. The starter and broadcast P ratesapplied for corn every other year were 40and 80 lb P2O5/A, respectively, for the hightesting site and 50 and 100 lb P2O5/A,respectively, for the low testing site. For thestrip-till and one-pass tillage practices, deepband P applications were made in the fall,prior to the corn crop, at rates of 40 and 50lb P2O5/A for the high and low testing sites,respectively. In the strip-till system, twotypes of band positions were tested. In thefixed band treatment [deep band (f)], theband was placed about 5 in. deep, with thestrip tiller in approximately the same placeprior to each corn year. In the random bandtreatment [deep band (r)], the placementswere offset by 8 in. between the two yearswhen they were applied. In the one-pass sys-tem, the fall band treatment was placedabout 5 in. deep in a band that ran at about


TABLE 2. Three-year average soybean yield responses (1998-2000) to residual P from starter fertilizer applied for corn the previous year on sites testing high and low in soil P.

Tillage for P application P2O5 applied, lb/A Grain yield, bu/ACorn Soybean method High P Low P High P Low P

No-till No-till None 0 0 53.2 36.7Starter 40 50 53.5 46.4

One-pass One-pass None 0 0 55.5 37.6Starter 40 50 55.7 47.3

Strip-till No-till None 0 0 53.5 38.3Starter 40 50 53.2 48.8

Chisel Chisel None 0 0 56.0 33.7Starter 40 50 56.2 50.4

Average None 0 0 54.6 36.6Starter 40 50 54.7 48.2

a 2º angle to where the corn row was plant-ed. This assured that the fertilizer band wasnot located continuously under the corn row,but varied from directly under the row to asmuch as 15 in. from the row.

After each corn year, soybeans (Pioneer91B64) were planted at a rate of 160,000seeds/A in 8 in. rows using a drill. No fertil-izer was applied to the soybeans to test theresidual effects of P applied in the previouscorn year.

Tillage EffectsThe effects of tillage on soybean yield

for both high and low P sites are shown inTable 1. At the low P site, there was no sig-nificant difference among the various tillagepractices, and average yield for the site was42.4 bu/A. On the high P site, soybeanyields were 2 to 3 bu/A higher where eitherdisk (55.6 bu/A) or chisel (56.1 bu/A) tillagehad been done compared to no-tillage.

In Table 1 and the following tables, thehigh P site exhibited higher overall yieldsthan the low P site. Although a statisticalcomparison between the two sites is beyondthe scope of this study, the higher yieldsassociated with the high P site are suspect-ed to be largely due to better P soil fertility.

Residual Effects of P Applied as aStarter Band

Soybean yield response to residual Papplied in starter fertilizer in the previousyear for corn areshown in Table 2.At the high P site,no response wasobserved for anytillage practice. Atthe low P site, sig-nificant responsesoccurred for alltillage systems.Yield increaseswere 9.7, 9.7, 10.5,and 16.7 bu/A forthe no-till, one-pass, no-till fol-lowing strip-till,and chisel tillage

practices, respectively. Corn grain yieldresponses behaved similarly for each tillagepractice. The overall response to starter,averaged across all tillage systems, was 11.6bu/A.

Testing the Efficiency of Banded PThe effects on soybean yield of reduc-

ing banded rates to half the recommendedbroadcast rates are shown in Table 3. At thehigh P site, there was no yield differencefrom residual P with either broadcast orbanded P applications. At the low P site,soybean yields from the broadcast P treat-ments were significantly greater (3.7 to 4.9bu/A) than yields from the starter P treat-ments. These data suggest that band appli-cations of P applied to corn at a half-rate tolow testing soils do not supply sufficientresidual P to optimize soybean yields in thefollowing year compared to broadcast appli-cations of P at the fully recommended rate.

Evaluating Residual Effects ofDifferent Band Placements of P

Soybean yield responses to residual Pfrom various band placements in the previ-ous corn year are shown in Table 4. At boththe high and low P sites, no significant yielddifference was detected between the resid-ual effects of P applied as starter or in deepbands in the one-pass tillage system. In no-till following the strip-till system, signifi-cantly lower soybean yields were produced


TABLE 3. Three-year average soybean yield responses (1998-2000) to residual P from starter and broadcast P applied to corn for one-pass and chisel cultivation tillage practices on sites testing high and low in soil P.


One-pass One-pass None 0 0 55.5 37.6Starter 40 50 55.7 47.3Spring broadcast 80 100 54.8 52.2

Chisel Chisel None 0 0 56.0 33.7Starter 40 50 56.2 50.4Fall broadcast 80 100 56.4 54.1

Average None 0 0 55.8 35.7Starter 40 50 56.0 48.9Broadcast 80 100 55.6 53.2

Researchers evaluated the responseof soybeans to fertilizer phosphorus(P) or potassium (K) placement and

rates, along with residual and direct-placed fertilization, over a two-year period(1995-1996). Studies (two P and two Ktests) were conducted on farmer fields with10-year histories of no-till. In addition, aP experiment was established on one ofIowa State University’s research farms.Treatments on farmer fields included tworates of P, 0 and 40 lb P2O5/A, or two ratesof K, 0 and 55 lb K2O/A, placement of fer-tilizer (surface broadcast or subsurfaceband 2 in. beside and 2 in. below the

seed), and time of fertilizer application.Treatments on the research farms weresimilar except the P fertilizer rates were 0,40, 80, and 160 lb P2O5/A.

Placement effects were variable forleaf P or K concentration, and grain yieldsfor broadcast P and K were as good as or better than banded applications.Researchers pointed out that there mightbe an advantage to applying P directly tothe soybean crop, at least when soil testlevels are optimum or lower.

Source: Buah, Samuel S.J., Thomas A. Polito,and Randy Killorn. 2000. Agron J. 92: 657-662.

Iowa: No-Tillage Soybean Response toBanded and Broadcast and Direct andResidual Fertilizer Phosphorus andPotassium Applications

R e s e a r c hN o t e s


from residual P when fall band locationswere offset from year to year [fall band (r)].No yield reductions were detected when Pwas placed in the same position during eachstrip tillage operation [fall band (f)].

SummarySoil test P level is an important factor

for understanding soybean yield responsesto residual P from various P placements andtillage practices. Placement is less of a con-sideration whensoil tests are high.However, whensoil tests are low,substantial yieldincreases may beseen from residualP applied eitherbroadcast or inbands the previousyear for corn.Reducing bandedrates to half therate recommended

for broadcast applications did not optimizeyields and overestimated the efficiency of Pbanding in this study.

Dr. Randall (e-mail: [email protected]) is Professor and Soil Scientist and Mr. Vetsch (e-mail: [email protected]) is Assistant Scientist,Southern Research and Outreach Center, Universityof Minnesota, Waseca, MN 56093-4521. Dr. Murrell(e-mail: [email protected]) is PPI NorthcentralDirector, located at Woodbury, Minnesota.

TABLE 4. Three-year average soybean yield responses (1998-2000) to residual P from starter and deep band P applied to corn for one-pass and no-till following strip-till practices on sites testing high and low in soil P.


One-pass One-pass None 0 0 55.5 37.6Starter 40 50 55.7 47.3Fall band 40 50 54.8 47.6

Strip-till No-till None 0 0 53.5 38.3Starter 40 50 53.2 48.8Fall band (f) 40 50 54.2 48.1Fall band (r) 40 50 54.6 43.9

each of the runoff plots. Six runoff studieswere conducted to determine the effects ofthe following treatments on P runoff:1. Soil test P (six levels of soil test P)2. Soluble P in poultry litter (four levels of

soluble P)


Non-point P runoff from pasturesreceiving animal manure applica-tions is believed to play an important

role in accelerated algal growth in nearbywater bodies. Therefore, concerns havearisen over proper P management.According to the Environ-mental Protection Agency(EPA) Concentrated AnimalFeeding Operations (CAFO)draft regulations, manureapplication rates for P maybe determined using soiltest P levels, threshold soiltest P levels, or a P Index(PI).

The original PI wasimplemented by the NaturalResources Conservation Ser-vice (NRCS) as a risk assessment tool for useacross the country. The PI combines theeffects of both P sources and P transport fac-tors in determining the risk of P runoff.Several states are now modifying the originalPI in order to better assess the risk of P lossin local regions. Some states are attemptingto determine threshold soil test P levelsabove which animal manures or commercialP fertilizer may not be applied due toincreased risk of P runoff. The objective ofthis study was to develop a PI for pastures inthe Ozark Highlands.

Calibration Using Small PlotsSeventy-two small runoff plots (5 ft. x

20 ft., 5 percent slope) were constructed ona Captina silt loam at the University ofArkansas Agricultural Research Station inFayetteville. Tall fescue was established on

Predicting Annual Phosphorus Losses from Fields Using the Phosphorus Indexfor PasturesB y P. B . D e L a u n e a n d P. A . M o o r e , J r .

A R K A N S A S

3. P in diet [normal diet,phytase, high availableP (HAP) corn, and phy-tase + HAP]

4. Fertilizer type [triplesuperphosphate (TSP;0-46-0) vs. poultry litter]

5. Poultry litter applica-tion rate

6. Timing (first runoffevent 1, 7, 21, or 49days after fertilization)

Rainfall simulators were used to pro-vide a 2 in./hr. storm event sufficient inlength to cause 30 minutes of continuousrunoff. Runoff water was collected and ana-lyzed for SRP.

In order to obtain a wide range of soiltest P levels, TSP was incorporated into 24plots during construction at rates equivalentto 0, 344, 687, 1,374, 2,061, and 2,748 lbP2O5/A. Although these rates are high forpasture and hay producers without access tomanure, the soil test P levels resulting fromthese rates are realistic and typically foundin pastures which have received annualpoultry litter applications for many years.

Small Plot Research ResultsStudy 1: Average soil test P levels

(Mehlich 3, 0- to 6-in.) were 233, 318, 439,609, 737, and 946 lb/A following additions

Runoff studies showed thatsoil test phosphorus (P) ispoorly correlated to solublereactive P (SRP) runoff con-centrations after P applica-tions of manure and com-mercial fertilizer have beenmade. Soluble P in the nutri-ent source was shown to bethe most important factoraffecting P loss.

of 0, 344, 687, 1,374, 2,061, and 2,748 lbP2O5/A. The first rainfall simulation wasconducted prior to any manure applica-tions. Results show that runoff P concen-trations are well correlated to soil test P(Figure 1a). Rainfall was applied to thesame plots one week later, and a similarrelationship was found (data not shown).Prior to the third rainfall simulation, poul-try litter was applied at rates equivalent to2.5 tons/A. No relationship was foundbetween soil test P and SRP runoff con-centrations after manure application(Figure 1b). However, a good relation-ship was found between SRP runoff con-centrations and SRP concentrations in thelitter applied (Figure 1c). These dataprovide evidence that P solubility of thelitter is much more important in regulat-ing P runoff than soil test P of recentlymanured fields.

Study 2: The effect of SRP in litterwas determined using various rates of alu-minum sulfate (alum). Mean SRP runoffconcentrations were 0.88, 13.4, 15.1, and26.0 parts per million (ppm) P for littertreated with 20 percent alum, 10 percentalum, 5 percent alum, and untreated litter,respectively (data not shown). Previousresearch (Self-Davis and Moore, 1998,Better Crops, Vol. 82, No. 4) has shownthat alum additions to poultry litterreduced SRP runoff concentrations.Increasing litter alum rates resulted inreductions in SRP concentration in runoff.

Study 3: Diet manipulated litterresulted in the highest SRP runoff con-centrations among all of the manure treat-ments. Total P application rates are listedin Table 1. Runoff P concentrations maybe expected to be highest fromplots receiving litter from the nor-mal diet due to a high total P con-tent. However, SRP runoff con-centrations were actually highestfrom the phytase and HAP corndiets (Table 1). This is becauseSRP concentrations in themanure were highest in the phy-tase and HAP corn diets.

These results show that SRP


Total P SRP SRP inapplied, applied, runoff,

Diet lb/A lb/A ppm

Normal 111.0 8.0 39.1HAP 83.9 13.7 65.9Phytase 66.5 17.9 84.6HAP + Phytase 56.3 4.5 36.5

TABLE 1. Phosphorus application rates and P runoff concentrations of different poultry diets.

0

1

2

3

4

0 200 400 600 800 1,000 1,200 1,400Mehlich 3, lb P/A

SRP

in ru

noff,

ppm

a

r2 = 0.86

0

5

10

15

20

25

30

0 200 400 600 800 1,000 1,200 1,400Mehlich 3, lb P/A

SRP

in ru

noff,

ppm

r2 = 0.00016

b

0

5

10

15

20

25

30

0 100 200 300 400 500 600Soluble P in litter, ppm

SRP

in ru

noff,

ppm

c

r2 = 0.82

Figure 1. Effect of soil P on SRP runoff concentra-tions with (a) no manure; (b) manure application; and (c) effect of litter P solubility on SRP runoff, based on small plotresearch using simulated rainfall.

Pasture PI DevelopmentThe PI for pastures, based on the tem-

plate initially proposed by the USDA-NRCS, is a multiplicative matrix thatincludes P source factors, P transport fac-tors, best management practices (BMPs),and a precipitation factor. The PI for pas-tures is calculated from the four terms as fol-lows:PI = (P sources) x (P Transport) x (BMPs) x(Precipitation)

Data from runoff studies discussedabove (Studies 1-5) were used to developweighting coefficients for P source factors

application rates are more impor-tant in affecting P runoff from pas-tures than total P application rates.Previous research studies havealso shown that P runoff fromperennial grass pastures is pre-dominantly of the soluble formbecause there is little erosion andminor loss of sediment-bound P.

Study 4: Mean runoff SRPconcentrations were 13.4, 26.0,and 103 ppm P for plots whichreceived alum-treated poultry lit-ter, normal poultry litter, and TSPat 160 lb P2O5/A (data not shown).This is expected since the P solu-bility of commercial fertilizer ismuch higher than that of animalmanures. As much as 94 percentof TSP is SRP whereas only 2 to 4percent of the total P in normal poultry litteris SRP.

Study 5: Runoff SRP concentrationsresulting from three rainfall simulationsincreased linearly with increasing poultrylitter application rates (Table 2). Soil test Plevels were similar for each of the plots.Mean SRP runoff concentrations for thethird rainfall simulation from plots receiving1 ton/A rates remained higher than that ofunfertilized controls, thus showing that solu-ble P of applied litter is an important factorin regulating P runoff even after three runoffevents.

Study 6: Mean runoff SRP concentra-tions were 3.0, 8.8, 14.3, and 17.6 ppm P for49, 21, 7, and 1 days until the first runoffevent occurred after litter application. Ifseveral small, non-runoff storm eventsoccurred before the first runoff event, then Prunoff could be greatly reduced. However,data on large fields show that as much as 12to 18 months may be needed to reduce Prunoff concentrations to background levels.Applying poultry litter at times having a lowP runoff risk, such as July or August, wouldalso be the worst period to apply withrespect to volatile ammonia nitrogen (NH3-N) loss. Therefore, results from this studywere not utilized to develop the P sourceterm of the PI for pastures.


Litter Rainfall simulation, application (Days after litter application)rate, tons/A 1 (<1) 2 (7) 3 (14)

0 1.2 0.9 0.91 8.8 5.2 4.82 16.6 8.9 5.43 27.8 14.9 8.24 33.0 20.0 8.8

TABLE 2. Runoff P concentrations (ppm) from variouspoultry litter applications rates.

Risk of P runoff PI rating Interpretation/recommendation

Low < 0.6 N basedMedium 0.6 - 1.2 N basedHigh 1.2 - 1.8 P basedVery high > 1.8 No P application

TABLE 3. Phosphorus Index for pastures – interpretation and recommendations.

Figure 2. Relationship between Mehlich 3 P and SRP runoff concentrations from rainfall simulations conducted in farmer pastures.

0

2

4

6

8

10

0 200 400 600 800 1,000 1,200Mehlich 3, lb P/A

Aver

age

SRP

in ru

noff,

ppm

P

r = 0.06

(soil test P and soluble P application rate).Multiple regression analysis showed weight-ing coefficients to be 0.000666 for soil test Pand 0.404 for soluble P application rate.

Transport factors include soil erosion,runoff class, flooding frequency, applicationmethod, application timing, and grazingmanagement. Based on the calculated PI,fields are assigned a class of low, medium,high, or very high potential for P movement.Once a high PI rating is achieved, it is rec-ommended that nutrients be applied at ratesno higher than current crop P needs.Furthermore, no P application should bemade on fields having a very high PI rating(Table 3).

Small Plot Validation of the PasturePI

Validation studies were conducted onsix farms of various forage cover and slope inArkansas and Oklahoma. Twelve small plotswere constructed on each farm, and portablerainfall simulators were used to provide a2.8 in./hr. storm event. Plots were built onvarious soil test P levels determined fromprevious intensive soil sampling. Poultry lit-ter was applied based on the PI for pasturesto half of the plots and NRCS guidelines (noPapplication with 0- to 6-in. soil test P > 300lb/A) to the other half. Litter was applied toprovide PI values ranging from low to high.Six runoff events were conducted on each ofthe 72 plots, three before litter application

and three afterwards. The average SRPrunoff concentrations from the six runoffevents at each farm were poorly correlated to0- to 6-in. soil test P (Figure 2). This trendis similar to that found in runoff studies inthe development of the PI. However, a muchbetter correlation was found between SRPrunoff concentrations and the PI for pastures(Figure 3). These results show that soil testP is a poor predictor of P runoff concentra-tions once manure is applied. The PI forpastures was a much better predictor of Prunoff than soil test P, showing that P appli-cations, as well as transport factors, shouldbe taken into account.

Watershed Validation of the PasturePI

Although the PI was shown to be a bet-ter predictor of P losses, these studies wereconducted on small plots under simulatedrainfall. Therefore, annual P loads (lbP/A/yr) were measured for two 1-acre water-sheds which had received litter applicationsannually since 1994. Each watershed ishydrologically isolated with earthen bermsand equipped with flumes and automatedwater samplers. Since soluble P applicationrates were recorded each year, the PI couldbe calculated. Runoff volume, runoff P con-centrations, and runoff P loads were measured each year. The relationshipbetween measured annual P loads and the PI


Figure 3. Relationship between the PI and SRP runoff concentrations from rainfall simulations conducted in farmer pastures.

0

2

4

6

8

10

0 0.5 1.0 1.5 2.0 2.5Phosphorus Index

Ave

rage

SRP

in ru

noff,

ppm

P

r = 0.77

Figure 4. Relationship between measured annual P load from one-acre, pastured water-sheds and the PI.

0

1

2

3

0 1 2 3Phosphorus Index

Mea

sure

d an

nual

Plo

ad, l

b P/

A/y

r.

r = 0.91

1:1 line

(continued on page 23)

erate Cl testing soils. The wheat cultivars were grown with and without 40 lbCl/A applied as KCl. The KCl was appliedas a pre-plant spring band.

Two trial sites were used in each of thethree years of the study, one a clay loam tex-

ture and the other a finesandy loam texture. Soil Cllevels were low in all yearsat the fine sandy loam siteand in 1996 and 1998 at theclay loam site (Tables 1and 2). A moderate soil Cllevel was recorded for theclay loam site in 1997. Soil

potassium (K) levels were determined andfound to be lower on the fine sandy loam soil(332 lb K/A in 1996, 288 in 1997, and 192in 1998), relative to the clay loam (732 lbK/A in 1996, 510 in 1997, and 680 in1998). Response of cultivars to Cl additionwere evaluated for their statistical signifi-cance and the ability to return C$1.50 foreach C$1.00 invested in fertilizer (fertilizereconomics). Using a wheat price ofC$4.00/bu and C$0.17/lb for Cl, this workedout to a 2.5 bu/A yield increase.

Few significant differences wereobserved in the Canadian and U.S. hard redspring wheat cultivars on the sandy loamsoil site (Table 1). Where significant differ-ences were recorded, addition of Cl didincrease grain yields. From a fertilizer eco-nomics evaluation, 17 of the 30 cultivar-years (three years x 10 cultivars) showed apositive response to Cl addition, 11 showedno yield difference, and two showed a yielddecline of more than 2.5 bu/A (Table 3).

Chloride (Cl) is one of the 17 essentialnutrients required for plant growthand development. Chloride plays a

major role in plant function, including pho-tosynthesis, enzyme activation, nutrienttransport, water movement in cells, stomatalactivity, accelerated plantdevelopment, reduced lodg-ing, and improved diseasesuppression and tolerance.

Chloride is a mobilenutrient in the soil likenitrate (NO3) and as suchcan move freely with the soilwater. Consequently, soil Cllevels can increase or decrease from year-to-year, depending on the water table and land-scape position used to collect soil samples.A soil Cl level less than 30 lb/A in the top 2ft. of soil is generally used as an indicationthat insufficient Cl is available for optimiz-ing grain yield of cereals. Levels of 30 to 60lb/A may provide a crop response, whilethose above 60 lb/A are unlikely to beresponsive.

Research across the Great Plains hasidentified that there is a strong varietalresponse of cereal crops to soil Cl levels. Toevaluate the effect of soil and fertilizer Cl onannual spring wheat cultivars common towestern Canada, a trial was conducted at theAgriculture and Agri-Food Canada BrandonResearch Centre between 1996 and 1998. Aselection of Canadian and adaptedAmerican hard red spring wheat varieties,along with Canada Prairie Spring, CanadaExtra Strong, and Canada Western AmberDurum varieties, were grown on low to mod-


M A N I T O B A

Spring Wheat Cultivar Response toPotassium Chloride FertilizationB y C y n t h i a A . G r a n t , D e b r a L . M c L a r e n , a n d A d r i a n M . J o h n s t o n

Increases in grain yieldoccurred frequently withpotassium chloride (KCl)application, but responsepatterns for cultivars werenot consistent from year toyear or location to location.

The cultivar AC Barrie was the only hard redspring wheat to consistently give aneconomic response. Other cultivars likeGuard showed a significant positive res-ponse in 1998, no difference in 1996, and aneconomic yield loss from Cl addition in1997. On average, all of the Canadian hardwheat cultivars showed a yield response of more than 2.5 bu/A on this sandy loamsoil, while only Pioneer 2375 was respon-sive amongst the U.S. hard wheat types(Table 3).

Significant positive responses wererecorded with the Canada Prairie Springwheat cultivar AC Karma and the AmberDurum cultivars Kyle and Plenty at this finesandy loam soil site (Table 1). While Claddition resulted in a large positive yieldresponse for AC Karma and Kyle in two

years, both cultivars showed a negative eco-nomic response in 1997 (Table 3). Resultswere equally variable among years forGlenlea and AC Taber. These results con-firm that crop response to Cl is not specificto low soil Cl levels alone, but is also influenced by the cultivar and the growing season. It is important to note that given thelow to medium soil test K levels at the sandyloam site, some of the yield responsesrecorded could be due to the K applied withthe Cl in the KCl fertilizer.

While Cl levels at the clay loam sitewere low to moderate in all years of thestudy, few significant grain yield responseswere recorded (Table 2). Considering allclasses of wheat in the study, only seven ofthe 45 cultivar-years (three years x 15 culti-vars) showed a significant positive response,


TABLE 1. Effect of cultivar and KCl treatment on grain yield on a fine sandy loam soil in 1996, 1997 and 1998, Brandon, MB.

Grain yield, bu/A1996 1997 1998

Cultivar -Cl p>f +Cl -Cl p>f +Cl -Cl p>f +Cl

Canada Western Red SpringAC Barrie 27.1 ns 34.6 37.5 ns 44.5 36.3 * 42.0CDC Teal 35.0 ns 34.3 32.4 ns 37.3 37.6 ns 41.4AC Cora 28.8 + 33.8 38.8 ns 37.7 32.1 ns 38.6AC Domain 28.1 ns 33.1 38.8 ns 37.8 35.9 * 44.3AC Majestic 29.9 * 40.8 38.1 ns 41.6 38.7 ns 39.8Roblin 27.1 ** 32.0 27.3 ns 30.2 31.5 + 33.2

U.S. Hard Red SpringGrandin 37.1 ns 31.6 38.2 ns 37.8 32.7 ns 37.5Pioneer 2375 32.7 ns 39.3 36.8 ns 39.0 41.4 ns 43.3Marshall 41.8 ns 41.4 37.0 ns 40.0 44.4 ns 45.0Guard 28.9 ns 28.9 32.2 ns 29.2 37.2 ** 43.4Canada Prairie SpringAC Karma 27.4 * 42.3 42.5 ns 37.7 38.3 + 45.0AC Taber 35.9 ns 29.9 40.1 ns 46.2 44.2 ns 48.3

Canada Western Extra StrongGlenlea 29.3 ns 25.4 33.2 ns 38.0 37.4 ns 39.2

Canada Western Amber DurumKyle 25.2 ns 32.6 39.0 ns 35.6 30.0 + 37.1Plenty 22.5 + 31.5 30.1 ** 37.6 36.4 ns 38.6

Soil test Cl (24 in.) 8 lb/A 10 lb/A 8 lb/A

ns, +, *, ** represent not statistically significant, and significant at p = 0.10, 0.05, and 0.01, respectively, usingorthogonal contrasts.


while five showed a significant negativeresponse to Cl addition. While AC Barrieshowed a strong response to Cl addition atthe fine sandy loam location, there was noresponse on the clay loam soil type. From afertilizer economics point of view, yieldresponses were small, with only 12 of the 45cultivar-years showing a positive response toCl addition (Table 3). There were sevencultivar-years where Cl addition reducedgrain yield by more than 2.5 bu/A, while thedifference was less than this in the remain-ing 26 cultivar-years. On average across thestudy years, grain yield responses of greaterthan 2.5 bu/A were only recorded with ACKarma and the two durum cultivars. Theseresults would indicate that while the soil Cllevels were low to moderate at this clay loamsoil site, response to KCl addition was con-

siderably less than on the fine sandy loamsoil location.

Increases in grain yield occurred fre-quently with KCl application, but the KClresponse patterns for cultivars were not con-sistent from year to year or location to loca-tion. Decreases in crop yield with KCl appli-cation occurred in some site-year-cultivarcombinations. The reason for the yielddepression was uncertain. Consistentincreases in grain yield with KCl applicationoccurred in the cultivar Karma, whichshowed positive response to KCl applicationin five of the six site-years. Due to the incon-sistency in the effects of KCl on grain yield,prediction of KCl response can be a chal-lenge. However, it appears as if some culti-vars, such as AC Karma, are more consistentin their response to KCl application than are

TABLE 2. Effect of cultivar and KCl treatment on grain yield on a clay loam soil in 1996, 1997 and 1998, Brandon, MB.

Grain yield, bu/A1996 1997 1998

Cultivar -Cl p>f +Cl -Cl p>f +Cl -Cl p>f +Cl

Canada Western Red SpringAC Barrie 52.5 ns 51.5 54.7 ns 54.5 45.3 ns 45.8CDC Teal 56.4 ** 51.2 57.3 ns 56.1 51.8 ns 53.9AC Cora 56.6 ns 56.5 52.6 ns 53.0 44.3 ns 45.9AC Domain 51.6 ns 52.9 50.8 ns 53.2 53.4 + 52.1AC Majestic 56.7 ns 59.5 50.2 ns 48.4 50.3 ns 51.9Roblin 47.6 + 44.0 51.4 ns 48.1 43.2 ns 43.4

U.S. Hard Red SpringGrandin 52.6 ns 52.1 60.1 ns 60.5 52.3 ns 51.4Pioneer 2375 60.3 ns 57.0 59.6 * 66.4 53.4 ns 53.8Marshall 60.6 * 56.7 61.9 ** 67.8 55.0 ns 52.0Guard 54.4 ns 54.9 57.0 + 62.8 57.0 ns 56.4

Canada Prairie SpringAC Karma 57.9 * 66.4 53.8 ** 64.0 56.6 + 62.9AC Taber 60.7 ns 60.3 58.6 + 55.0 60.9 ns 58.7

Canada Western Extra StrongGlenlea 57.6 ns 58.8 54.6 ns 59.6 61.8 ns 60.1

Canada Western Amber DurumKyle 61.2 ns 63.9 61.9 * 69.2 51.2 ns 50.1Plenty 65.2 ns 67.1 68.6 ns 72.5 51.8 ns 57.3

Soil test Cl (24 in.) 8 lb/A 44 lb/A 18 lb/A

ns, +, *, ** represent not statistically significant, and significant at p = 0.10, 0.05, and 0.01, respectively, usingorthogonal contrasts.


TABLE 3. Spring wheat grain yield response to Cl fertilizer (40 lb Cl/A) addition across the sites and years in Brandon, MB.

Fine sandy loam Clay loam1996 1997 1998 Mean 1996 1997 1998 Mean

Cultivar Yield response, bu/A

Canada Western Red SpringAC Barrie 7.5 7.0 5.7 6.7 -1.0 -0.2 0.5 -0.2CDC Teal -0.7 4.9 3.8 8.0 -5.2 -1.2 2.1 -1.4AC Cora 5.0 -1.1 6.5 3.5 -0.1 0.4 1.6 0.6AC Domain 5.0 -1.0 8.4 4.1 1.3 2.4 -1.3 0.8AC Majestic 10.9 3.5 1.1 5.2 2.8 -1.8 1.6 0.9Roblin 4.9 2.9 1.7 3.2 -3.6 -3.3 0.2 -2.2

U.S. Hard Red SpringGrandin -5.5 -0.4 4.8 -0.4 -0.5 0.4 -0.9 -0.3Pioneer 2375 6.6 2.2 1.9 3.6 -3.3 6.8 0.4 1.3Marshall 0.4 3.0 0.6 1.3 -3.9 5.9 -3.0 -0.3Guard 0.0 -3.0 6.2 1.1 0.5 5.8 -0.6 1.9

Canada Prairie SpringAC Karma 14.9 -4.8 6.7 5.6 8.5 10.2 6.3 8.3AC Taber -6.0 6.1 4.1 1.4 -0.4 -3.6 -2.2 -2.1

Canada Western Extra StrongGlenlea -3.9 4.8 1.8 0.9 1.2 5.0 -1.7 1.5

Canada Western Amber DurumKyle 7.4 -3.4 7.1 3.7 2.7 7.3 -1.1 3.0Plenty 9.0 7.5 2.2 6.2 1.9 3.9 5.5 3.8

the majority of the cultivars evaluated in thisstudy.

Dr. Grant (e-mail: [email protected]) works insoil fertility and Dr. McLaren is a plant patholo-

gist at the Brandon Research Centre of Agricultureand Agri-Food Canada, Brandon, Manitoba. Dr.Johnston (e-mail: [email protected]) is PPIWestern Canada Director, located in Saskatoon,Saskatchewan.

is shown in Figure 4. Results show thatthe PI for pastures closely predicted annu-al P loads from pastures receiving naturalrainfall and poultry litter applications(r=0.91). These results confirm that the PIfor pastures predicts P loads well underfield conditions with natural rainfall.

SummarySince P runoff from perennial pas-

tures is predominantly soluble P, the SRPconcentration in the source and theamount applied are more important than

the total P content of the source.Validation studies showed the pasture PIpredicts annual P losses very well fromfields receiving natural rainfall.

Mr. DeLaune is Senior Graduate ResearchAssistant, University of Arkansas. Dr. Moore isAdjunct Professor of Agronomy and USDA-ARSScientist, Department of Crop, Soil and Envi-ronmental Sciences, University of Arkansas,Fayetteville. Phone (501) 575-2354; fax (501)575-7465.

Phosphorus Index...(continued from page 19)

2001 Number 4

Potash & Phosphate InstituteSuite 110, 655 Engineering Drive

Norcross, Georgia 30092-2837

PeriodicalsPostage

I can’t believe it. Thirty-five years just flashed in front of my eyes. It couldn’t havebeen that long since Pat and the kids and I piled all our worldly possessions into a (small)U-Haul trailer hitched to our old Mercury and headed to Atlanta for my first real job. We wereuneasy about leaving Auburn University. We had set roots and established an extended fam-ily base among fellow graduate students during our nearly four years there. We were uncer-tain about the future.

Well, things have turned out just fine. As Pat and I make final preparations to leaveAtlanta...on our way to retirement, we count ourselves blessed for having had the opportuni-ty to spend 35 years in the fertilizer industry. My work has taken us from Auburn to Atlantato Albany, Georgia, to Stillwater, Oklahoma, and back to Atlanta. Along the way, we havebeen privileged to travel to such diverse places as China, Australia, and France...and hadthe opportunity to meet, work with, and become friends with some of the finest people in theworld.

One of the most difficult assignments in my career has been writing this pagein Better Crops with Plant Food for the past couple of years. I’m humbled becausethere could never be another who frames his or her words in a more eloquent manner thandid the late Dr. J. Fielding Reed, former PPI President. Between 1983 and 1999 he ownedthis space. Yet, it’s a special honor for me to share the podium with Fielding.

This will be my last column as Executive Vice President of the Institute.However, Dr. David Dibb, PPI President, has asked me to continue with the page, so I hopeyou will visit me here for a while longer. In the meantime, I wish to express my appreciationto all my co-workers at PPI past and present. They have been the biggest reason...along withfolks like Lance Murrell, Don Ball, Billy Darnell, Bob Westerman, and scores of other col-leagues...that my job has been the best there is.

Pat says for me to not go around inviting everybody to come and see us at Amelia Island,Florida. I won’t do that, but if you’re ever in the area...

What Happened to 1966?

IN THIS ISSUE

• Soybean Responseto ResidualPhosphorus forVarious Placementsand TillagePractices

• Soil PhosphorusMay Be Importantto Beef HerdHealth andPerformance

• Predicting AnnualPhosphorus Lossesfrom Fields Usingthe P Index forPasturesand much more...

what happened to 1966? - international plant nutrition ...webindex... · china s.s. portch, hong...

Documents