Environmental Benefits of Improved Grazing Management
by Robert Hendershot, Grassland Management Systems Conservationist, Natural Resources Conservation Service
The environmental benefits of well managed pasture, include reduced soil erosion; improved air and water quality; better plant diversity, vigor and production; and improved fish and wildlife habitat. Improving grazing management will result in more complete vegetative cover and improved soil structure that will allow a higher percentage of the rainfall to infiltrate the soil where it can be used for plant growth rather than running off where it can result in soil erosion and sedimentation problems. The ecological processes increase including decomposition of manure in a highly managed pasture. Nutrients can then be recycled several times during the growing season. The overall soil quality improves with improved grazing management.
Water quality improves as the pasture vegetation becomes denser and the soil conditions improve. A University of Wisconsin study showed that pastures are the best "crop" for reducing runoff, erosion, and phosphorus pollution over any other land use. A similar study done by USDA- Agricultural Research Service, North Appalachian Experimental Watershed, Coshocton Ohio revealed that both surface and ground water in the pastured watershed was just as good or better than water leaving the adjacent pristine wooded watershed. This study compared an unimproved typical beef cow-calf pasture. Seventeen cow-calf pairs grazing 64 acres, set stocked, no rotation put on in the spring, removed in the fall and feed hay all winter. The pasture was not grazed for two years before the research started and has a small stream beginning and running through the watershed. It served as the only water source for the animals. The surface water tested at 0.5 PPM nitrate before the cattle grazing started and 0.7 PPM after, with safe drinking water standards being 10 PPM. This pastured watershed has 17 percent of the rainfall runoff were as the adjacent comparison wooded watershed yielded a 25 percent runoff with a 1.2 PPM nitrate. Pasture soils are a terrific biological filter to recover nutrients passing through the soil. Grass roots are active nearly year-round and thus can recover nutrients efficiently from pasture soils that can leach from other land uses.
Water Quality emphasis is shifting to non-point sources of pollution. Many grazers are surprised to learn just how good pastures are from an environmental standpoint. Grazers need to understand that their system of farming when reasonably managed is among the best from a water quality and soil erosion standpoint in mainstream agriculture. Ohio has a hydrologic research station where agriculture practices can be studied for their impact on soil erosion, surface water and ground water quality. Dr. Lloyd Owens is a research scientist for the Agricultural Research Service that operates the North Appalachian Experimental Watershed near Coshocoton, Ohio in cooperation with the Ohio State University. Dr. Owens has been collecting data from a variety of pasture systems for over 20 years. There was a greater infiltration of rainfall in pastures than the wooded areas. When a fence was added to exclude livestock from the stream and water was provides from another source, annual soil loss from the pasture was reduced from 70.4 tons on the 64 acres (1.1 tons per acre) to 38.4 tons (0.6 ton per acre). This pasture includes slopes from 2 to 35% on soils that are predominately silt-loam. Though it was not measured directly it is apparent that the soil losses must have been very high on the stream banks when the animals used the stream as the water source.
In another area, 25 cow-calf pairs rotationally grazed 42 acres which was divided into 4 paddocks. One of the paddocks served as a winter feeding area where hay was fed November through April made from other locations on the farm. The soils is this area were silt loams surface texture with a 0.37 K value and a T value of 4. The slope ranges from 12 to 25 percent, average 20 percent. The soil loss from the wintering area was 1 ton per acre per year with 60 percent of the loss occurring during the winter. This compares to soil losses on a similar measured watershed of 2.9 tons per acre per year for conventional-tilled corn planted on the contour. The winter paddock was severely trampled by late March and appeared to be severely damaged. The paddock always recovered and was grazed in May. Rotating the wintering area would have reduced soil losses and would have better distributed the manure nutrients. Ohio Natural Resources Inventory results have shown a declined since 1982 in pastureland soil erosion rates. The erosion rates on Land Capability Class VII pastureland were eroding over 5 tons per acre per year in 1987.
Pasture systems reduce the time that livestock spend in confinement, thus reducing the concentrated manure control problems. Manure is more evenly distributed with management intensive grazing than with feedlots where there is potential manure odor and control concerns as well as with unmanaged pastures were animals concentrate manuring near shade or watering sites. Manure is generally dispersed about the pasture in a properly managed system. This combined with the low runoff rate creates a low potential for nutrient runoff.
The third pasture system had 35 cow-calf pairs grazing 59 acres. There were 4, 8.5 acre summer paddock of orchard grass and 4, 6.25 acre tall fescue paddocks grazed in the winter and hay fed that was made from the paddocks. The soil loss from this system was very low only 0.1 ton per acre. These pasture received 200 pounds of N fertilizer applied annually in three equal applications in April, June and August. This rate of nitrogen resulted in surface runoff with average nitrate-N levels of 3 and 4 PPM for the summer and winter paddocks. The groundwater nitrate level rose above 10 PPM in both but was higher in the winter paddocks. The winter paddock received an additional 300 pounds of nitrogen in hay that was brought in as winter feed. Legumes were interseeded into the fescue and orchardgrass, nitrogen fertilizer was then discontinued, but the P and K fertility levels were maintained. The cow numbers were also reduced from 35 to 25. It took several years for the nitrate nitrogen levels to drop to less than 10 PPM. The nitrate-nitrogen levels in the ground water dropped to less than 10 PPM in the winter paddocks and to less than 3 PPM in the summer paddocks. The most likely times for high nitrate concentrations to occur in runoff are within a few days following fertilizer application. The best management practice is to avoid applying fertilizer before major storm events. Maintaining good soil health and plant residual after grazing to reduce potential runoff will also help reduce nitrate-nitrogen losses.
Pasture because of its permanent and diverse plant cover provides increased shelter and food for wildlife as well as the grazing animal. Properly managed pastures can provide nesting habitat by delaying mowing and leaving adequate plant reserves for rapid growth. Most ground nesting birds and rabbits prefer the management intensive grazing system. Research is showing that grazing animals can be used to manage the vegetation on stream banks to enhance the fish populations. Studies done in Minnesota, Wisconsin and Canada have resulted in management intensive grazing systems becoming the recommended conservation practice to manage stream banks on farms to control the overgrowth and enhance fisheries. Fish numbers were 2 to 3 times higher where cattle grazed in a management intensive grazing system than where cattle where totally excluded from the stream. Some recent research done on the impacts grazing animals have on streams have studied:
- Time in the water and voiding
- Preferred crossing points
- Alternative water supplies
- Bacteria in streamflow
- Grazing cattle and riparian ecosystems
Catle generally access watercourses for drinking or crossing, but seldom lounged in the water as they do in ponds. If the cattle are standing in the stream and not drinking there is another livestock husbandry concern. Cattle have preferred crossing points. They do not like soft or mud creek bottoms, they prefer solid footing. When a good rock bottom crossings are constructed cattle will cross at that point and leave other areas alone. Crossing and access points should be designed to allow easy crossing and provide limited access for drinking. When given a choice cattle were observed to drink from a spring-fed water trough 92 percent of time compared to drinking from a stream. Cattle will generally do most of their grazing within 800 feet of a water source. Designing and spacing watering tanks can keep grazing animals away from stream and increase grazing utilization of the pasture. Clean water is important for good animal performance. Providing good clean water from a spring or well can increase gains by 20 percent. Rotational grazing supports more diverse bird communities, more amphibians and were just as good as grassy buffers in regards to bank stability and in-stream habitat.
Grassland soils are a great reservoir for organic carbon. The rise in carbon dioxide levels in the atmosphere over the past 100 years, from 290 parts per million to 345 in 1986, had led, in part to the so-called "Greenhouse Effect". (Council on Environment. Qual. and Wild) The greenhouse effect is the warming of the Earth's lower atmosphere due to increased levels of some gases, primarily carbon dioxide, that allows incoming short-wave radiation from the sun to reach Earth, but absorb the outgoing long- wave radiation from the Earth's surface back out to Space. The top meter of soil, world-wide, contains nearly double the carbon of that contained in the vegetation it supports and in the atmosphere. Soil organic carbon is extremely stable having radiocarbon ages that average 1450 years in the top ten inches of soil to ages that increase from 2000 years to 12,100 years at ever increasing soil depths to 90 inches. (Wild)
The plant community that exists on a soil can play a big role in the amount of carbon stored in the soil. Total organic carbon is twice as abundant in prairie soil as in a forest soil, all other soil forming factors being equal. Grassland soils also contain more organic carbon with depth then do forest soils. (Jenny) Better then half of the organic matter produced in a forest ecosystem is contained in the above-ground portion, while in a grass ecosystem over 90% of the organic matter produced exists in the roots.
Any initiative that supports grassland agriculture will, over the long term, support an effective carbon sink. Grasses and legumes use atmospheric carbon as plant tissue building blocks. The unutilized and undecomposed plant tissue (primarily roots) is returned to the soil and becomes part of the soil's carbon pool. This process helps reduce atmospheric levels of carbon dioxide. A permanent grassland environment stores more soil carbon then does cropland agriculture. After 100 to 200 years of cropping, the organic matter content of the prairie soils in North Central and Great Plains states has decreased to one half to one third of the original level. (Kilmer) In, England a forested soil, formerly cropped, was returned to permanent sod. After 100 years, the soil carbon content of the upper 10 inches had doubled from 1.4 percent to 3.0 percent. Fifty percent of this increase occurred within the first 20 years. (Wild)
Prescribed grazing management includes the following best management practices:
- Flash grazing riparian areas (12 to 48 hours)
- Grazing systems based on forage availability and demand(measure the forage available and determine the animal intake)
- Proper stocking rates (know the yield potential for the grazing area and adjust for weather patterns)
- Proper rest periods between grazing events (10 to 16 days in the spring 28 to 42 days in the summer)
- Proper time period (avoid soil compaction)
- Have drinking water available close to the grazing livestock (water distribution is an important part of a grazing system)
Well managed grazing systems provide a healthy soil and clean water and air for people wildlife and fish. Managed grazing systems can be part of a profitable farm operation by lowering cost, improving herd health and reducing labor.
Robert Hendershot, Grassland Management Systems Conservationist
USDA-Natural Resources Conservation Service
Phone 740-653-1559 extension 32
Council on Environmental Quality, Environmental Trends, Executive office of the President, Washington, DC, 1989, 62.
Jenny, H., Factors of Soil Formation, MCGraw Hill, New York, NY, 1941, 222
Kilmer, V. J., Handbook of Soils and Climate in Agriculture, CRC Press, Boca Raton, FL, 1982, 211-219
Wild, A., editor, Russell’s Soil Conditions and Plant Growth, Eleventh Edition, Longman Scientific and Technical, New York, NY, 1988, 588-592
Water Quality from Pasture, Dr. Lloyd Owens and Hank Bartholomew, Ohio State University Extension.
Follett, R. F., J. M. Kimble, R. Lal, The Potential of U.S. Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect, Lewis Publishers, New York, 2001