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Improving soil health and productivity on marginal lands using managed grazing livestock
Beyond grazing, managed grasslands can provide ecological services with indirect and direct economic benefits that offer an incentive for multi-functional uses that provide the opportunity to increase available grazing lands. Increasing biodiversity of the plant community may maximize primary production by optimizing utilization of available light, water, and nutrient resources, enhance forage nutritive value for grazing livestock, improve nutrient retention while reducing nutrient leaching or loading in surface run off, enhance stability of production in response to disturbance, increase soil organic matter, reduce invasion of exotic species, and provide wildlife feed and habitat. Strategically managed grazing may increase biodiversity of cool season pastures by creating disturbance in the established plant community through diet selection and treading as well as increased nutrient cycling and dispersal of plant seeds. Soil organic matter will increase carbon and nutrient sequestration and water-holding capacity of soils and is greater in grazed pastures than land utilized for row crop or hay production. Studies evaluating the effects of grazing management on soil organic matter in the eastern and central United States are limited. However, greater soil organic matter has been observed in cool season pastures grazed by management intensive than continuous grazing or grazed by mob or strip grazing than ungrazed grasslands. In addition to organic residues, pasture forages provide roots that produce macropores mitigating compactive forces on soils. The reduced soil compaction and increased surface structure provided by plant shoots and residues increase water infiltration. Therefore, water infiltration in cool season pastures managed to maintain 10 cm residual height did not differ than ungrazed pastures which limits nonpoint source pollution of surface water resources and provides resilience to floods and droughts. Through increased diversity of the plant community, productivity of selected species, and nutritive quality of the forage with alterations of habitat structure, grazing systems can be developed that enhance habitat for wildlife and insect pollinators. Although grazing management may enhance the ecological services provided by grasslands, environmental responses are controlled by variations in climate, soil, landscape position, and plant community resulting in considerable temporal and spatial variation in the responses. Furthermore, a single grazing management system may not maximize both forage quality for grazing livestock and each of the potential ecological services provided by grasslands. Therefore, production and ecological goals must be integrated to identify the optimal grazing management for an individual site.
Keywords: grazing, biodiversity, ecological services