Management Strategies to Minimize the Impacts of Grazing on Non-point Source Pollution of Pasture Streams in the Midwest

J.R. Russell1, D.A. Bear1, K.A. Schwarte1, and M. Haan2

1Iowa State University, Ames, IA2Michigan State University, Hickory Corners, MI

IMPAIRMENTS TO IOWA’S WATER RESOURCES2008 Impaired Waters List (357 streams & 77 lakes)

(Iowa DNR, 2008)

PHOSPHORUS DELIVERY TO THE GULF OF MEXICO (Alexander et al., 2008)

http://water.usgs.gov/nawqa/sparrow/gulf_findings/

HYPOTHETICAL ROUTES OF NONPOINT SOURCE POLLUTION BY GRAZING CATTLE

Direct manure deposition Stream bank erosion

Surface run-off

FACTORS CONTROLLING THE EFFECTS OF GRAZING ON WATER QUALITY

• Location of grazing• Timing of grazing• Intensity of grazing• Length of grazing

(CAST, 2002)

MODEL FOR QUANTIFYING THE EFFECTS OF GRAZING MANAGEMENT ON NONPOINT SOURCE

POLLUTION OF PASTURE STREAMS

Pollutant concentration or frequency

Cattle #s Grazing Days Stream Length

Cow-days/ftDiet intake and indigestibility

Fecal Pollutant Load or Incidence

DistributionGrazing management

Plant speciesShade distribution

Stream Riparian zone

Open area Congregation area

Transport inrunoff

Transport in runoff

Stream

ClimateOff-stream water

EFFECTS OF PASTURE SIZE ON THE CONGREGATION OF GRAZING COWS IN AND WITHIN 100 ft OF A PASTURE

STREAM OR POND ON SIX PASTURES OVER THREE YEARS

0.0

10.0

20.0

30.0

40.0

50.0

0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0

Total Pasture Size, ha

GP

S R

ea

din

gs

wit

hin

th

e W

ate

rsid

e Z

on

es

,%

of

To

tal

GP

S R

ea

din

gs

y = 35.4 - 0.83x + 0.005x2 (r2 =0.61)

IMPLICATIONS OF PASTURE SIZE AND SHAPE ON CATTLE TEMPORAL/SPATIAL DISTRIBUTION

RESEARCHRef. (State) Approx.

pasture size, ac

Treatment Est. distance from

treatment to stream, ft

Stream and/or

riparian effects

Sheffield et al., 1997 (VA)

35 - 54 Offstream water

37 Reduced congregation

Porath et al., 2002 (OR)

30 Offstream water

1600 Reduced congregation

Byers et al., 2005 (GA)

42 Offstream water

296 Reduced congregation

“ 35 Offstream water

263 No significant effect on

congregation

Agouridis et al., 2005 (KY)

5 – 7.5 Offstream water

230 No effect on congregation

Line et al., 2000 (NC)

104 Offstream water

338 No effect on NPSP

PERCENTAGE OF TIME GRAZING CATTLE ARE IN

AND WITHIN 110 ft OF A PASTURE

STREAM IN TWO YEARS

30 ac pastures463 ft stream reach

(Haan et al., 2010)

CSU = Continuous stocking unrestricted

EFFECT OF RESTRICTING

STREAM ACCESS TO STABILIZED

CROSSING ON CONGREGATION OF CATTLE IN OR NEAR PASTURE STREAMS

IN TWO YEARS(Haan et al., 2010)

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restricted

EFFECT OF RESTRICTING

STREAM ACCESS BY ROTATIONAL

GRAZING ON CATTLE

CONGREGATION IN OR NEAR PASTURE STREAMS IN TWO

YEARS(Haan et al., 2010)

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

EFFECT OF SHORT-TERM ACCESS TO

OFFSTREAM WATER AND MINERAL

SUPPLEMENTATION ON CONGREGATION OF

CATTLE IN OR NEAR PASTURE STREAMS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedw/W or open = with offstream water and mineral

EFFECT OF OFF-STREAM WATER OR RESTRICTED STREAM ACCESS ON CONGREGATION OF CATTLE WITHIN 110 FT OF A PASTURE STREAM IN 10 (small)

OR 30 (large) ACRE PASTURES OVER 5 MONTHS (2010)

IMPLICATIONS OF PASTURE SIZE AND SHAPE ON CATTLE TEMPORAL/SPATIAL DISTRIBUTION

Regulatory

•Treatments to control NPS of pasture streams seem likely to be most effective on small or narrow pastures.

Probability of cattle presence within 110 feet of a pasture stream over the temperature range

EFFECT OF THE TEMPERATURE-HUMIDITY INDEX ON THE AMOUNTS OF TIME CATTLE WERE IN THE

RIPARIAN AREAS OF BERMUDAGRASS-TALL FESCUE PASTURES WITH OR WITHOUT OFFSTREAM WATER

(Franklin et al. 2009)

EFFECTS OF AMBIENT TEMPERATURE ON THE PROBABILITY OF COWS SEEKING SHADE

Percent of the total time cattle spent within the stream zone by interval

Distribution of pasture shade

• Cattle in pastures with more shade within the stream zone spent more time in the stream zone

Pasture Total ShadeShade Within Stream Zone

Shade Within Streamside Zone

Shade Within Riparian Zone

acres % of total shade

CSUW large 0.96 3.7 10.2 13.9

CSU large 1.13 1.5 21.1 22.6

CSR large 2.08 0.0 1.1 1.2

CSUW small 0.33 10.7 30.0 40.7

CSU small 0.60 2.9 39.7 42.5

CSR small 0.56 0.2 1.1 1.2

EFFECTS OF GRAZING MANAGEMENT ON NONPOINT SOURCE POLLUTION OF

PASTURE STREAMS

EFFECTS OF GRAZING MANAGEMENT ON ANNUAL EROSION/DEPOSITION ACTIVITY AND NET EROSION

OF STREAM BANKS IN 2008 AND 2009

EFFECTS OF STOCKING RATE

BETWEEN BIMONTHLY MEASUREMENTS OF THE PROPORTION OF BARE AND MANURE-COVERED GROUND

WITHIN 50 FT OF STREAMS IN 13

PASTURES0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Period Cow-days / stream m

Ave

rag

e B

are

Gro

un

d,

%

0.0

0.5

1.0

1.5

2.0

2.5

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Period Cow-days / stream m

Man

ure

-Co

vere

d G

rou

nd

, %

y = 10.4 + 3.73x – 0.314x2 (r2 =0.16)

y = 0.1 + 0.18x – 0.009x2 (r2 =0.35)

GRAZING SYSTEM EFFECTS ON PROPORTIONS OF BARE AND MANURE-COVERED GROUND

WITHIN 15 TO 110 FT OF PASTURE STREAMS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

GRAZING SYSTEM EFFECTS ON PROPORTIONS OF APPLIED PRECIPITATION AND AMOUNTS OF SEDIMENT AND P

TRANSPORTED IN RUNOFF FROM SIMULATED RAIN APPLIED TO BARE AND VEGETATED SITES ON STREAMBANKS AT 7.5 cm/hr

(P < 0.10)

a a

a

a

a

a

bb

bb

bb

cc

c

CONTRIBUTIONS OF PRECIPITATION RUNOFF, DIRECT FECAL DEPOSITION, AND CUT BANK EROSION TO

ANNUAL SEDIMENT LOADING OF PASTURE STREAMS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

CONTRIBUTIONS OF PRECIPITATION RUNOFF, DIRECT FECAL DEPOSITION, AND CUT BANK EROSION TO

ANNUAL SEDIMENT LOADING OF PASTURE STREAMS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

CONTRIBUTIONS OF PRECIPITATION RUNOFF, DIRECT FECAL DEPOSITION, AND CUT BANK EROSION TO

ANNUAL PHOSPHORUS LOADING OF PASTURE STREAMS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

CONTRIBUTIONS OF PRECIPITATION RUNOFF, DIRECT FECAL DEPOSITION, AND CUT BANK EROSION TO

ANNUAL PHOSPHORUS LOADING OF PASTURE STREAMS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

GRAZING SYSTEMS EFFECTS ON

STREAM BANK EROSION

SUSCEPTIBILITY (1 – 60) AND

VEGETATION (1 – 4) SCORES OVER

FIVE YEARS

CSU = Continuous stocking unrestrictedCSR = Continuous stocking restrictedRS = Rotational stocking

ROLE OF GRAZING CATTLE ON PATHOGEN LOADING OF PASTURE

STREAMS

STOCKING RATE EFFECTS ON MEAN CONCENTRATIONS OF TOTAL COLIFORMS IN BIWEEKLY WATER SAMPLES FROM UP- AND DOWNSTREAM SAMPLING SITES IN 13

PASTURES OVER 3 YEARS

STOCKING RATE EFFECTS ON THE INCIDENCES OF BOVINE ENTEROVIRUS (BEV), CORONAVIRUS (BCV), AND ROTAVIRUS (BRV) IN BIWEEKLY WATER SAMPLES FROM

STREAMS IN 13 PASTURES FOR THREE YEARS

BEV: y = 1.98+0.017x-0.00089x2 (r2=0.0101)

BCV: y = 2.54+0.41x-0.015x2 (r2=0.0345)

BRV: y = 0.27+0.11x-0.0020x2 (r2=0.0708)

EFFECTS OF PRESENCE OR ABSENCE OF CATTLE IN PASTURES FOR 0 TO 6 DAYS PRIOR TO SAMPLING ON THE INCIDENCES OF

BOVINE ENTEROVIRUS, CORONAVIRUS, AND ROTAVIRUS IN UP- OR DOWNSTREAM WATER SAMPLES FROM 13 PASTURES FOR 3 YEARS

INCIDENCE OF BOVINE ENTEROVIRUS AND CORONAVIRUS SHED BY 90 GRAZING COWS IN 3

MONTHS OVER TWO YEARS(No E. coli O157:H7 or Bovine rotavirus shed)

INCIDENCE OF BOVINE ENTEROVIRUS IN RUNOFF FROM RAINFALL SIMULATIONS ON STREAM BANKS OF PASTURES WITH

UNRESTRICTED STREAM ACCESS IN TWO YEARS

(No E. coli O157:H7, Bovine coronavirus, or Bovine rotavirus observed)

CONCLUSIONS

• Stream bank erosion is primarily related to hydrologic processes that supersede possible grazing effects

• Improper grazing management may increase:– Bare ground near pasture streams– Manure concentration near pasture streams– Sediment and nutrient loading of precipitation runoff

• Pathogen loading of pasture streams by grazing cattle is:– Poorly related to presence of total coliforms

• Bovine enterovirus may be a better indicator– Confounded by upstream loading

• Domestic and wildlife species– Rare and controlled by:

• Seasonal incidence of shedding of the pathogens• Manure distribution• Transport of the pathogens to the stream

CONCLUSIONS

• Risks of grazing on nonpoint source pollution of pasture streams may be controlled by maintaining streamside vegetation by use of:– Stabilized crossings with riparian buffers– Rotational grazing– Off-stream shade? – Off-stream water and/or nutrient supplementation???

CONCLUSIONS

• The Best Management Practices to control nonpoint source pollution on individual pastures will be site specific.– Small, narrow pastures will likely need more restrictive

practices to control distribution of grazing cattle than large, wide pastures

– Other characteristics to consider• Cattle stocking rate• Cattle breed, age, and physiological state• Distance to off-stream water• Shade distribution• Botanical composition• Stream order and evolution

Acknowledgements:• This project is supported in part by:

• The Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Award No. 2006-51130-03700 •The Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Award No. 2007-35102-18115•The Leopold Center for Sustainable Agriculture•Iowa Beef Center•Rathbun Land and Water Alliance