Grazing Management of Beef
Cows to Limit Non-point
Source Pollution of Streams
in Midwestern Pastures
Doug Bear
Iowa State University
Department of Animal Science
Animal Science 426
October 15, 2008
Land Regulations
• 1901
– USDA developed principles to regulate grazing within forage
reserves
• Grazing was allowed if it did not damage water supplies
• 1934
– Taylor Grazing Act
• Placed all public lands, not controlled by the US Forest Service, into
grazing districts controlled by the Grazing Service Department in the
Department of the Interior
• Later became the Bureau of Land Management (BLM)
• BLM charged with halting overgrazing and soil destruction through
Grazing Management Plans
• 1969
– National Environmental Policy Act
• All agencies required to write environmental impact statements for
all major federal actions that might affect the environment
• BLM required to write statements for all local grazing programs
• 1985
– Food Security Act
• Developed the Conservation Reserve Program (CRP)
– Took row cropland in highly erodible areas out of crop production
and seeded with forages for an annual payment
– Contracts lasted 10 to 15 years
– Forage couldn’t be grazed or harvested unless federal emergency
was declared
– Effects
» Seeded large amount of land in forage
» Reduced soil erosion and water pollution while increasing
wildlife habitat
» Inflated price of local crop and pastureland
Water Regulations
• 1973
– Clean Water Act
• Goal
– Restore and maintain the chemical, physical, and biological integrity of
the nation’s waters
• Defined point source and nonpoint source pollution
– Point source pollution
» Water pollution from facilities that discharge to water resources
through a discernible confined and discrete conveyance including
but not limited to a pipe, ditch, channel, tunnel, conduit, well,
discrete fissure, container, rolling stock, concentrated animal
feeding operation, or vessel or floating craft from which pollutants
might be discharged
» May be controlled by technology-based approaches
» Point source rules prohibit discharge of pollutants from a point
source to waters of the US except as authorized by a NPDES
permit (National Pollution Discharge Elimination System)
» Point sources specifically include Concentrated Animal Feeding
Operations (CAFOS) and regulated by the CAFO rules
– Nonpoint source pollution
» Water pollution whose source can not be identified
» Represents 60 to 80% of water pollution today
» Usually occurs over a broad area
» Technology-based controls are inadequate
» Controlled by Best Management Practices (BMP’s)
» Regulated by Total Maximum Daily Load (TMDL) regulations
•
1999
– Unified National Strategy for Animal Feeding Operations
• Developed by EPA and USDA
• Goal is that all Animal Feeding Operations (AFO’s) develop and
implement Comprehensive Nutrient Management Plans (CNMP’s)
– The largest 5% of AFO’s would be required to develop a CNMP by EPA as
part of the NPDES permitting process
– The remaining 95% of the AFO’s would be expected to develop a CNMP
voluntarily using locally focused incentive programs
– CNMP should have:
» A Feed Management Plan
» A Manure Storage and Handling Plan
» A Land Application Plan
•
2002
– New CAFO regulations implemented
IMPAIRED WATER SOURCES
• Definition
– Any water source that can not meet the standards
for its designated use for:
• Drinking
• Contact
• Recreation
• Extent
– 366 impaired water bodies in Iowa (2006)
NUMBERS OF IOWA WATER SOURCES WITH
DIFFERENT IMPAIRMENTS (2006)
Iowa Agriculture
• Land Use
– 91.3% IA land in
agriculture
– 15.7% IA agriculture
land in Conservation
Reserve Program
(CRP)
• Cattle
– 7th in US cattle
production
• 92,000 beef cow/calf
pairs
<http://extension.agron.iastate.edu>
<http://www.usda.gov>
ANNUAL SEDIMENT, PHOSPHORUS, AND
NITROGEN LOADING OF ROCK CREEK LAKE FROM
TRIBUTARIES WITH DIFFERENT PROPORTIONS OF
PASTURELAND (Downing et al., 2000)
S e d im e n t
T o ta l P
T o ta l N
6 .0
5 .0
60
50
4 .0
40
3 .0
30
2 .0
20
1 .0
10
0
W a te r s h e d 1
10
15
20
2
25
3
30
35
40
P a s tu r e , % o f to ta l la n d
45
P and N, kg/ha
Sediment, MT/ha
70
•
ENVIRONMENTAL
CONCERNS IN
SURFACE WATERS
Sediment
– Turbidity
– Siltation
– Clogs waterways
– Flow alterations
– Loss of aquatic habitat
– Transports nutrients to water
bodies
– Diminishes water quality for
human consumption
– Loss of recreational uses
• Phosphorus
– Stimulates algae growth
– Turbidity
– Reduced aquatic life
– Presence of toxins
– Loss of recreational uses
• Bacteria
– Human and livestock health
concerns
– Reduces recreational opportunities
Sources of Pollutants
• Upland
– Pollutants arise over an
extensive area
– Non-point Source
Pollutants
– Move with surface runoff
• Rainfall, Snowmelt
•
Stream Channel
– Direct deposition of urine
and feces
– Stream bank erosion
• Removal of forage along
stream banks
• Trampling of stream
banks and streambeds
FACTORS CONTROLLING THE EFFECTS OF
GRAZING ON WATER QUALITY
•
•
•
•
Location of grazing
Timing of grazing
Intensity of grazing
Length of grazing
GRAZING CATTLE AND RIPARIAN AREAS
• During periods of heat stress, grazing cattle may
seek shade or water in pastures for
thermoregulation.
• Cattle congregating in riparian areas may
contribute to sediment, nutrient, and pathogen
loading of surface waters.
• Management and pasture characteristics may
alter the effects of climate on cattle distribution
within a pasture.
QUESTIONS
• What are the effects of grazing
management practices and climatic
conditions on the distribution of cattle
in pastures?
• If cattle distribution in pastures can be
altered through grazing management,
what are the effects of this on
sediment, nutrient and pathogen
loading of pasture streams?
Grazing Management Practices
• Adjust stocking rate within pasture
• Provide an offstream water source
– Better grazing distribution within pastures
• Utilize forage
– Opportunity for cattle to not travel to
streams
• Treading damage?
• Pathogens?
• Mineral feeders
• Shade location within pastures
• Forage species characterization
RHODES RESEARCH
FARM
• 6 – 30 ac pastures
– Smooth Bromegrass
– Reed Canarygrass
• 462-ft stream section
bisected each pasture
• 15 Fall-calving Angus cows
per pasture
– Mid-May to Mid-October
– Initial body weights
• 2005 (1428 lb)
• 2006 (1271 lb)
• 2007 (1366 lb)
GRAZING
MANAGEMENT
•
•
Continuous stocking - unrestricted
stream access (CSU)
Continuous stocking - stream access
restricted to a stabilized crossing
(CSR)
– Crossing
• 18-ft wide
• Geofabric, polyethylene webbing, and
crushed rock
– Riparian buffer
• 2.25 ac
•
Rotational stocking (RS)
– Upland paddocks
• Four 6.95 ac paddocks
• 50% forage removal
– Riparian paddock
• One 2.25 ac paddock
• Maximum 4 days stocking or minimum
sward height of 4 inches
STREAM CROSSINGS
Fall 2004
Summer 2007
Fall 2006
Summer 2008
GPS
COLLARS
• One cow per pasture
– AgTrax GPS collar (BlueSky
Telemetry, Aberfeldy, Scotland)
– 2 weeks per month from May
through September in 2006 and
2007
– Cattle position recorded at 10
minute intervals 24 hours per
day.
• During the second week, offstream water available
– May, July, and September
– CSU and CSR pastures
– Off-stream water sites located a
minimum distance of 700 ft.
from the stream on both sides of
the stream.
PASTURE ZONES
Upland Zone
• > 220 ft. from stream
• 86.8% of pasture
Transition Zone
• 110-220 ft. from stream
• 6.1% of pasture
Riparian Zone
• 0-110 ft. from stream
• 6.1% of pasture
Stream Zone
• Within stream
• 1.0% of pasture
MICRO-CLIMATE
• A data logging HOBO weather
station (Onset Comp. Co.,
Bourne, MA)
– Centrally located within riparian
area.
– Ambient temperature, black globe
temperature, wind speed, and
relative humidity recorded at 10 min
intervals.
– Temperature humidity index (THI),
black globe temperature humidity
index (BGTHI), and heat load index
(HLI) were calculated for every 10
min measurement.
Table 1. Calculation of Microclimatic Indices.
THI1
BGTHI2
HLI3
1
THI = [0.8×Temp] + [(RH÷100) × (Temp− 4.4)] + 46.4
BGTHI = [0.8×BGtemp] + [(RH÷100) × (BGtemp−14.4)] + 46.4
HLIBGTemp>25 = 8.62 + (0.38× (RH÷100)) + (1.55×BGTemp) − (0.5×WS) + [e2.4−WS]
HLIBGTemp<25 = 10.66 + (0.28 × (RH ÷ 100) ) + (1.3 × BGTemp) − WS
Temperature Humidity Index. Temp (°C), RH (%). Mader et al., 2006.
Black Globe Temperature Humidity Index. BGTemp (°C), RH (%). Mader et al., 2006.
3
Heat Load Index. BGTemp (°C), RH (%), WS (m/s), e = 2.71828. Gaughan et al. 2008.
2
CATTLE IN RIPARIAN AREA –
GPS COLLAR
GPS Readings, % Total
12
a
10
8
6
4
2
trt
mth
trt×mth
b b
a
b
b
Stream
<0.05
0.06
0.11
Riparian
<0.05
NS
NS
0
Stream
Riparian
Pasture Zone
Riparian Zone
3
GPS Readings, % Total
GPS Readings, % Total
Stream Zone
2.5
2
1.5
1
0.5
0
May
June
July
August
September
Bars with different letters differ (P<0.05).
16
14
12
10
8
6
4
2
0
May
June
July
August
September
Probability of Cattle Within The Riparian Area
EFFECT OF TEMPERATURE ON CATTLE
USE OF THE RIPARIAN AREA
CSU
(12.1% / °C)
CSR
(5.8% / ºC)
Temperature, ºC
CSU = Continuous Stocking Unrestricted Stream Access
CSR = Continuous Stocking Restricted Stream Access
Probability of Cattle in Shade
EFFECT OF TEMPERATURE ON
CATTLE USE OF PASTURE SHADE
(20.7% / °C)
Temperature, ºC
Pooled CSR and CSU pasture data.
EFFECT OF OFF-STREAM WATER ON
CATTLE USE OF THE RIPARIAN AREA
Stream Zone
Riparian Zone
4
GPS Readings, % Total
a
GPS Readings, % Total
3.5
3
2.5
2
1.5
b
1
b b
0.5
0
May
Trt
Mth
Water
Trt × water
Mth × water
Trt × mth × water
July
September
Stream
Riparian
<0.05
<0.05
NS
NS
<0.05
0.08
<0.05
NS
0.09
NS
NS
NS
16
14
12
10
8
6
4
2
0
May
July
September
Lake Rathbun Watershed
Chariton
http://geology.com/state-map/iowa.shtml
Farm and pasture characteristics
Farm
name
Area
(acres)
Cattle
breeds
Water
source
%
fescue
Farm A
309.4
Angus
Stream
22.8
Farm B
160.4
Angus
Ponds
24.8
Farm C
227.8
Angus
Cross
Stream &
ponds
48.6
Farm D
52.6
Angus
Stream
7.8
Farm E
33.4
Mexican Stream &
ponds
Corriente
40.0
GPS collars
• Spring, summer,
and fall seasons
• 2 – 3 cows / farm
• Duration
– Up to 2 weeks
• Recorded locations
at 10 min intervals
Representative photo of GIS buffers
Water source
50 ft.
100 ft.
©Iowa State University & MIT
MCNAY FARM – August 2007
Stream- 1.0%
50- 6.1%
100- 5.9%
200- 8.4%
Uplands- 78.7%
©Iowa State University & MIT
% of observations cows located in
water source
Percent of observations of cows
located in water source by farm
2.25
2
1.75
1.5
1.25
1
0.75
0.5
0.25
0
Farm A
Farm B
Farm C
Farms
P > 0.10
Farm D
Farm E
% of observations cows located in
riparian buffer
Percent of observations of cows
located in riparian area by farm
45
a
40
35
ab
ab
30
b
25
20
b
15
10
5
0
Farm A
Farm B
Farm C
Farm D
Farms
P < 0.08
Riparian area expressed as water source + 15.2m + 30.5 m
Farm E
Effect of season on the proportion of time
cattle were within a water source
2.5
% of Observations
2
1.5
1
0.5
0
Spring
Summer
Season
P < 0.14
Fall
Estimated probability of cows within
riparian area as affected by temperature
Est i m
at ed Pr obabi l i t y
0. 7
Point Estimate: 1.048
0. 6
Estimated
probability
of cattle in
riparian
area
0. 5
0. 4
0. 3
0. 2
0. 1
0. 0
- 10
0
10
20
Tem
p
Temperature (°C)
30
40
Distribution of shade on farms
Riparian shade
Pasture shade
Name
% of
riparian area
% of total
pasture shade
% of pasture
area
Farm A
75.8
31.5
57.8
Farm B
67.2
2.8
59.6
Farm C
79.1
44.8
30.5
Farm D
68.0
21.0
72.8
Farm E
55.5
58.4
27.2
*Riparian area expressed as water source + 15.2m + 30.5 m
Proportion of cattle observations in riparian
area as affected by the proportion of total
pasture shade in riparian area
% of observations
30
20
Spring
Summer
Fall
10
0
1
11
21
31
41
Riparian shade, % of total pasture shade
Spring: y=2.09+0.75x-0.009x2 ; (p<0.01); (r2=0.75)
Summer: y=10.58-0.08x+0.005x2 ; (p<0.14); (r2=0.19)
Fall: y=11.04-0.33x+0.010x2 ; (p<0.04); (r2=0.37)
51
61
Proportion of cattle observations in riparian
area as affected by the proportion of riparian
area in total pasture
40
% of observations
35
30
25
Spring
20
Summer
15
Fall
10
5
0
1
3
5
7
9
11
13
15
17
19
21
23
25
% riparian area in pasture
Spring: y=0.29+1.62x-0.04x2 ; (p<0.01); (r2=0.76)
Summer: y=9.83-0.80x+0.05x2 ; (p<0.003); (r2=0.63)
Fall: y=11.60+1.95x+0.09x2 ; (p<0.001); (r2=0.92)
27
29
31
Estimated probability of cows within riparian
area as affected by temperature
Est i m
at ed Pr obabi l i t y
0. 6
+++ Farm A (24.3%)
0. 5
Estimated
probability
of cattle in
riparian
area
+++ Farm B (2.5%)
+++ Farm C (17.2%)
0. 4
+++ Farm D (22.4%)
0. 3
+++ Farm E (28.7%)
0. 2
0. 1
0. 0
- 10
Far m
Al l ey
0
G
i bbs
10
p
TempTem
(°C)
Har m
an
20
M
cNay
30
40
Schul t z
Erosion Pin Collaborators
Chariton
McNay
©Iowa State University & MIT
Proportion of bare ground on stream
banks within 50 feet of streams
2007 Average bare ground by months
% of bare ground within 50 ft of streams
40.00
35.00
30.00
25.00
May
July
September
November
20.00
15.00
10.00
5.00
0.00
A
B
C
D
E
F
G
F
H
I
J
K
L
M
Annual soil erosion in relation to annual
cow-days per stream foot
Annual soil erosion, inches
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
2
4
6
8
Annual cow-days/ft stream
10
12
Proportion of fecal covered ground on stream
banks within 50 feet of streams
2007 Average fecal covered ground by months
% of fecal covered ground within 50 ft of
streams
2.25
2.00
1.75
1.50
May
July
September
November
1.25
1.00
0.75
0.50
0.25
0.00
A
B
C
D
E
F
G
Farms
H
I
J
K
L
M
Management Costs
• Stream Crossing
• Installation - $4,347 + Labor
• ~$150-200 for rock (replacement)
• Fencing
• High-tensile, 5 strands, electric - $0.70 / ft, 25 year
• High-tensile, 2 strands, electric – $0.59 / ft, 25 years
• Water System
• Pipe, Water Tanks, Installation, Hydrants - $2.30 / ft
IMPLICATIONS
• Cattle presence in streams can be reduced
through improved grazing management.
–
–
–
–
Rotational Stocking
Improved Access / Crossing Points
Off-Stream Water Sources
Shade Away From Pasture Streams
• Altering cow distribution may reduce or
negate impacts of grazing on riparian areas
• The Best Management Practice to limit
damage to the riparian area of a given pasture
is likely to be site specific
QUESTIONS???
Acknowledgements:
• 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 and 2007-3510218115
• Iowa Department of Natural Resources (US EPA 319 Program)
• Leopold Center for Sustainable Agriculture
Additional information:
Iowa Beef Center – www.iowabeefcenter.org
Jim Russell – jrussell@iastate.edu
Doug Bear – dbear@iastate.edu