The Effects of Grazing
Management on Water Quality
Kirk Schwarte
Iowa State University
kirksch@iastate.edu
Materials and Methods
• Six, 30 acre, cool season
grass pastures
– Two blocks, three
treatments
• Continuous stocking with
unrestricted stream
access (CSU)
• Continuous stocking with
restricted stream access
(CSR)
• Rotational stocking (RS)
– Bisected by a 463 ft reach
of stream that flows year
round
CSR
CSU
CSR
RS
CSU
RS
Effects of Poorly Managed Grazing
• Cattle congregate near water
sources
– Disturb banks
• Shear force from hooves break down
bank structure
– Increases surface runoff
• Increases soil bulk density
• Promotes sediment, phosphorus, and
pathogen loading
– Decrease streamside vegetation
• Decreases stream shade
• Increases stream width to depth ratio
• Decreases ‘erosion resistance’ by plants
Non-Point Source Pollution
Runoff
Bacteria
Pathogens
Sediment
Water Quality
Water Clarity
Phosphorus
Nitrogen
Algae
Aquatic Plants
Die / Decompose
Oxygen
Impaired
Waters
Aquatic
Life
Hypoxia /
Eutrophication
Impaired Waters
• Any stream or body of water that can not be used its
designated use (drinking, recreation, fishing, aquatic
life…etc.)
• Increased from 279 (2006) to 439 (2008).
– 40% of increase can be linked to change in standards
• Streams
– Major causes are bacteria, invertebrates, and pollutant caused
fish
• Lakes
– Major causes are pH, algae, turbidity, and bacteria
http://www.igsb.uiowa.edu/wqm/wqa/303d/2008/2008FinalListFactSheet.pdf
Phosphorus Delivery to the
Gulf of Mexico
http://water.usgs.gov/nawqa/sparrow/gulf_findings/
Interesting:
• 2009 Hypoxic zone
shrank by half
• Agriculture usually cited
as main source of water
nutrients
•Army Corps of Engineers
project to make habitat for
endangered Pallid Sturgeon
•548 million tons of soil
•358,403 lbs of P
•40-60,000 acres in 5ft of
slurry
(Feedstuffs, 2010)
Surface Runoff
Percent Runoff
0.8
0.7
0.6
%
Slopes ranged from
3.4° to 33°, with the
average of 13°
0.5
0.4
0.3
0.2
0.1
0
CSU Vegetative
CSU Bare
CSR Vegetative
RS Vegetative
RS Bare
Treatm ent
Sward Height
12
10
8
cm
6
4
2
0
CSU Vegetative
CSU Bare
CSR Vegetative
Treatment
RS Vegetative
RS Bare
Sediment/Phosphorus Surface Runoff
Sedim ent
3000
Lbs/acre
2500
2000
1500
1000
500
0
CSU Veg
CSU Bare
CSR Veg
RS Veg
RS Bare
Treatm ent
Phosphorus
14
12
10
Lbs/acre
8
6
4
2
0
CSU Vegetative
CSU Bare
CSR Vegetative
Treatm ent
RS Vegetative
RS Bare
Stream Bank Erosion
• Majority of erosion caused by the hydrology of
the stream, not cattle
– Cut banks and Oxbows
• Freeze/thaw during winter months
Stream Bank Erosion
Net Erosion
Net Erosion
10
9
8
7
6
6
5
4
3
2
1
cm
cm
10
9
8
7
5
4
3
2
0
CSU
CSR
1
0
RS
Treatment
2005
2006
2007
Year
Erosion Activity
Erosion Activity
25
20
20
15
15
cm
cm
25
10
10
5
5
0
0
CSU
CSR
Treatment
RS
2005
2006
Year
2007
Incidence of Pathogens in Grazing
Beef Cattle
• Likelihood of
pathogens in the GI
tract of cattle is high
– Shedding is highly
variable
• Believed to be
dependent on stress
(calving / heat)
Pathogens
• E.coli 0157-H7
June
August
September
2007
0%
0%
15.6%
2008
0%
0%
0%
2009
0%
0%
0%
Fecal Pathogens
2008
June
2009
B. Coronavirus 0%
0%
B. Rotavirus
0%
0%
B. Enterovirus 1%
39%
August
September
1%
0%
0%
0%
29%
19%
0%
0%
0%
0%
41%
13%
Runoff Pathogens
2008
2009
April
June
August
October
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
2
0
E.Coli 0157:H7
B. Coronavirus
B. Rotavirus
B. Enterovirus
Mean Concentrations of Fecal Coliforms in
Upstream and Downstream Samples from
Pastures in the Lake Rathbun Watershed
Upstream
Downstream
2000
1500
1000
500
No
v
ct
O
Se
pt
Au
g
Ju
ly
Ju
ne
ay
M
Ap
ri l
ar
c
h
0
M
Fecal coliforms, CFU/100 ml
2500
Management Practices
•
•
•
•
Off-stream water
Rotational/Flash grazing
Riparian Buffers
Off-stream Shade
Off-Stream Water
• Water
– 8-12 gal. for maintenance
– 20-25 gal. during hot weather
– Lactating > Dry Cows
• Water should located no greater than 800 ft.
from the animals for efficient grazing
• Effects of off-stream water will differ based on
weather conditions
Pasture Management Guide, Iowa State University
Proportion of time spent within 110 ft zone when
comparing the availability of an alternative water
Source
16.0
14.0
12.0
10.0
Time within Zone,
%
CSU Open
8.0
CSU Closed
6.0
CSR Open
CSR Closed
4.0
2.0
0.0
May
June
July
Month
August
September
Riparian Buffers
• Complete
exclusion from
riparian areas
• Requires off-site
water or stream
crossing
• Eligible for
government
payments?
Probability of cattle being within the streamside zone in pastures with
continuous stocking with unrestricted stream access (CSU),
continuous stocking with restricted stream access (CSR)
E s t i ma t e d P r o b a b i l i
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
t y
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01
00
0.30
Estimated
Probability
P= 0.0663
CSU
CSR
11.9%
8.2%
0.00
0
10
20
30
T e mp e r a t u r e ,
Ce l s i u s
Temperature, C
T r e a t me n t
CS R
CS U
40
Rotational/Flash Grazing
• Brief grazing periods of highly erodible ground to
utilize forage, but maintain bank integrity and
water quality.
– Spring grazing
– Late summer grazing
• Managed to maintain sufficient forage height (4
inches) in riparian areas.
– Minimize surface runoff
– Maintain plant density
Mean proportions of time that cattle spent within the 110 ft zone of
pastures with continuous stocking with unrestricted stream access (CSU),
continuous stocking with restricted stream access (CSR), or rotational
stocking (RS) during the 2008 grazing season.
14
12
10
Time within Zone, %
a b
8
6
CSU
CSR
ab
4
RS
ab
ab
RS Riparian
Paddock
2
0
May
June
July
August
September
Month
a = differences between CSU and CSR
b = differences between CSU and RS
(P < 0.10)
*RS riparian paddock was stocked for a total of 6
days throughout the grazing season, or 4.3% of time
from mid May through September.
Off-stream Shade
• Cattle seek shade during the hot summer
days
– Allows for a place for cattle to congregate and
rest away from water sources
– May ease pressure on grasses near the
stream from high foot traffic
Stream Bank Forage
Bank Sward Ht
Cm
20
15
CSU
10
CSR
RS
5
0
May
June
July
August
September
October
Month
%
Bank Bare Cover
60
50
40
30
20
10
0
CSU
CSR
RS
May
June
July
August
Month
September
October
Pasture Size and Shape
• Many pastures were developed on highly
erodible land near streams
• If the pasture has a large percentage of
the pasture in a riparian area, cattle don’t
have anywhere else to go
• Even at cool temperatures, cattle will be
found near the water source
Pasture Size and Shape
% of Pasture
in Riparian
Area
E s t i ma t e d P r o b a b i l i t y
0. 42
0. 40
Farm A- 24.3
0. 38
0. 36
Farm B- 2.5
0. 34
0. 32
Farm C-17.2
0. 30
0. 28
Farm D-22.2
0. 26
0. 24
Farm E- 28.7
0. 22
0. 20
0. 18
0. 16
0. 14
0. 12
0. 10
0. 08
0. 06
0. 04
0. 02
0. 00
- 10
0
10
20
30
T e mp
Far m
Al l e y 1
Ha r ma n 2
Al l e y 2
Mc Na y 1
Gi b b s 1
Mc Na y 2
Gi b b s 2
Sc h u l t z 1
Ha r ma n 1
Sc h u l t z 2
40
Farm A1 +++
Farm B1 +++
Farm C1 +++
Farm D1 +++
Farm E1 +++
Farm A2 +++
Farm B2 +++
Farm C2 +++
Farm D2 +++
Farm E2 +++
•Treatments to control NPS of pasture streams
seem likely to be most effective on small or
narrow pastures.
Environmental Quality Incentives
Program (EQIP)
• Provides support to landowners to implement
programs that will benefit the conservation of our
nature resources
• Provides assistance in building fences, wells and
water sources, stream crossings, grass seeding,
and more…
Fencing
Two strand high tensile
fence for rotational grazing
and livestock exclusion
$0.68/ft
Four or more strands of
barbed wire for rotational
grazing and livestock
exclusion
$0.88/ft
Fencing must be maintained for 10 years, property line
fences are not covered.
ftp://ftp-fc.sc.egov.usda.gov/IA/Programs/FY09PracticeDescriptionsPaymentRates.pdf
Ponds
Ponds constructed by
making a dam, an
embankment, or
excavating to provide
water to livestock only.
$0.95 - $1.50/cub.yd. for
construction
$2.25 - $2.63 for repair
Must be maintained for 20 years and built to store
35 years worth of sediment
ftp://ftp-fc.sc.egov.usda.gov/IA/Programs/FY09PracticeDescriptionsPaymentRates.pdf
Prescribed Grazing
To improve and maintain $40 - $80/acre
desired species, plant
vigor, and plant quality
A one time payment with
to maintain a healthy
a maximum of $50,000.
herd, quality surface and
subsurface water,
reduce soil erosion, and
improve soil conditions
Other grazing practices must be followed and documented
before a payment is received.
ftp://ftp-fc.sc.egov.usda.gov/IA/Programs/FY09PracticeDescriptionsPaymentRates.pdf
Stream Crossings
For the construction of a Rock- $22.25/cub.yd.
culvert/bridge type
stream crossing for
Tube and Installationlivestock and small
$1,500 each
equipment
Typically a 50’ length x
24” diam. tube
Maintained for 10 years and landowner must get all
construction permits
ftp://ftp-fc.sc.egov.usda.gov/IA/Programs/FY09PracticeDescriptionsPaymentRates.pdf
Well and Water Tank
To drill a hole to form an $13.00/ft
aquifer
-Non-potable water
-6” or less diameter pipe
- 20 years
A tank or water trough to Varies… $0.38/gal
provide water for
animals
-Can also cover the
pump
ftp://ftp-fc.sc.egov.usda.gov/IA/Programs/FY09PracticeDescriptionsPaymentRates.pdf
IMPLICATIONS
• Stream bank erosion seems primarily related to stream
hydrology.
• Coliform and pathogen loading of pasture streams
comes from numerous sources including wildlife and
humans.
• Improper grazing management may increase:
– Bare ground near pasture streams
– Manure concentration near pasture streams
– Sediment and nutrient loading of precipitation runoff
• Risks of grazing on pasture streams may be controlled
by:
– Stabilized crossings with riparian buffers
– Rotational grazing
– Off-stream water
• Greatest risk of NPS pollution from grazing occurs in
small and/or narrow pastures.
Questions?
This material is based upon work supported by the Cooperative State
Research, Education, and Extension Service, U.S. Department of
Agriculture, under Award No. 2006-51130-03700. Any opinions, findings,
conclusions, or recommendations expressed in this publication are those
of the authors and do not necessarily reflect the view of the U.S.
Department of Agriculture.