By Steve Boyles
The environmental benefits of well-managed pasture include:
- reduced soil erosion,
- improved air and water quality,
- better plant diversity, vigor, and production,
- improved fish and wildlife habitat.
Improving grazing management will result in more grass 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 resulting in soil erosion and sedimentation problems. The ecological processes, including decomposition of manure and increase 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 with Pasture Quality
Water quality improves as the pasture vegetation becomes denser and the soil conditions improve. A university 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 USDAat Coshocton, Ohio, revealed that both surface and ground water in the pastured watershed was as good as, or better than, water leaving the adjacent wooded watershed. 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.
Grazing Management Systems
Management of the leaf area is important to sustain the plant’s persistence and future growth. The plant after being grazed must have enough leaf area to intercept sunlight for photosynthesis. The potential yield of a pasture is based on the amount of leaf area available for light interception. These leaves have a life span of about 30 to 60 days. Older leaves do not utilize the sunlight as well as younger leaves. This is one reason why under grazed or unmowed pastures decline. To manage a pasture well it is necessary to graze off half of the leaves to improve light penetration, which will encourage new leaf growth and keep the plant actively growing in a vegetative stage.
Set Stocked Grazing
Set stocked or continuous grazing is a system where the animals are maintained on a single pasture during the grazing season. This system allows the animals to selectively graze, unless the stocking rate is too high. If the animal numbers or the pasture size is not adjusted as pasture conditions change, this system will lead to some plants being overgrazed and others under grazed. Loss of desirable forage species, the invasion of weeds, erosion, and the uniform distribution of manure by the grazing animals are the management concerns.
Rotational Grazing
Rotational grazing systems have multiple pastures. An example would be a four-pasture system in which the animals graze a pasture for 7 to 10 days then are rotated to the next pasture. This system does allow for some rest period during the growing season for the plants. The actual length of the grazing time and rest periods depend on the size of the herd and the pasture and the weather. The pasture plants benefit from the rest with more growth and vigor, and animals gain from a more stable and nutritious forage supply. Manure is spread more uniformly by the grazing animals than in a continuous grazing system.
A well planned and operated grazing system:
- improves the vegetative cover, reducing erosion and improving water quality
- increases harvest efficiency, forage utilization
- increases forage quality and production
- rotating also evenly distributes manure nutrients.
Management-Intensive Grazing
Management-intensive grazing differs from conventional grazing systems in that livestock are moved frequently among pasture divisions called paddocks or cells. The animals are moved based on forage quality and quantity and livestock nutritional needs. This system provides a rest or recovery period for the growing plant and the soil. This system does not need to be a labor-intensive system, but it is a management-intensive system. The frequency, intensity, timing, and duration of grazing events, as well as the livestock stocking rate and the class of animals, will affect the ecosystem and the land management.
Access Roads
Livestock lanes or access roads can aid in livestock movement or the transportation of livestock feed. Access roads that are properly planned will allow for livestock and vehicle movement. Livestock can be moved from paddock to paddock with lanes much easier than by moving through paddocks. Livestock will tend to stop moving when they enter a new paddock and start to graze even though you may want them to move on to a different paddock. Grassed lanes can be grazed with adjacent paddock. The locations of lanes should avoid potential erosion, concentrated water flow, wet areas, and flooding. Avoid placing lanes up and down hills in wetlands or on organic soils. Stabilized lanes can be prepared for heavy traffic areas, areas subject to erosion, or unstable areas with geotextile fabric, a suitable subgrade material, and fine material on top to protect the animals’ hooves.
Stream Crossings
A stream crossing will control animal and vehicles crossing the stream. It can also be used to control access point for livestock watering. Pastures with streams have areas where the animals have chosen spots to cross the stream. These areas are usually the best locations to construct the stream crossing. The animals choose these areas because of stable footing and ease of crossing. Improving the existing crossing with the livestock’s needs in mind will encourage the livestock use. Livestock avoid soft, muddy, and rocky streambeds. They prefer a firm gravel bottom to walk on. They need to be able to see the bottom in order to use the area as a water source.
The primary component of a stream crossing is a heavy layer of gravel thick enough to support the animals. The size of the gravel affects how long the cattle spend in the crossing. Aggregate with about 1.50 inch diameter is large enough (that is, uncomfortable enough) to keep the animals from loitering but small enough to allow the animals access. The flow of the stream has to slow enough not to wash the aggregate away. Geotextile material can be used in streams with unstable streambeds. Stream crossings should be at least 10 feet wide. The ramps entering and exiting the channel should not be steeper than 4:1 slope (rise:run).
Alternatives to Stream Exclusion
One area of concern in grazing management is the impact of pasture management on streams within the pasture. Streams with continuously stocked and overgrazed pastures often have little vegetation on the banks and are wide, shallow, and muddy. These types of pastures have an erosion concern and nutrient run off into the stream. Complete exclusion of the livestock from the stream seems to be the solution, but the winding nature of many of the streams, flood damage to the fence, and the need for livestock water make complete exclusion impractical.
There are other alternatives to fencing livestock out of streams. These include rotational and management-intensive grazing systems that provide alternative water sources. Wisconsin studies have shown that rotational grazing systems can be an alternative to grassy buffer strips in regard to bank stability and in-stream habitat. Virginia Tech research concluded that the presence of an off-stream water source for grazing cattle reduced the time cattle spent near the stream. Cattle given a choice will drink from a spring-fed water trough 92% of the time compared to drinking from a stream. Providing an alternative source of good clean water in a trough and adequate forage will reduce stream bank erosion, sediment and sediment-bound pollutants, including nitrogen, phosphorus, and fecal bacteria. Mineral feeders and feed troughs should be some distance away from streams.
Ohio had a research station where agriculture practices can be studied for their impact on soil erosion, surface water, and groundwater quality. There is a greater infiltration of rainfall in pastures than in the wooded areas. When a fence is added to exclude livestock from the stream and water is provided from a trough, 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 (.6 tons per acre). This pasture includes slopes from 2% to 35% on soils that are predominantly silt-loam.
Livestock Use Area Protection
These are protected areas that are paved with asphalt or concrete or constructed with, and surfaced with, aggregate. These areas are designed to protect the pasture, soil, and water quality from being abused. Pastures can be pugged, or trampled, by the grazing animals during the spring or other extended wet periods. This trampling can lead to plant death or thinning of the stand. The resulting mud can reduce animal performance. Mud 4 to 8 inches deep will reduce gain by 14% and mud 8 to 24 inches deep will reduce gain by 25%. The damaged pastures are susceptible to soil erosion. Run off from damaged pastures can degrade surface waters with sediment and manure. Excessive soil compaction will reduce rain infiltration and plant growth.
Livestock heavy use areas or pads should be located outside the flood plains. If the pad is located close to a watercourse, run off and manure from the pad should be managed to protect the stream from pollution. These areas should be located at least 300 feet away from neighboring residences and away from wells. A manure management system should be designed to handle any accumulated manure on the pad.
Source : osu.edu