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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGING WATER AVAILABILITY AND QUALITY TO MAINTAIN OR INCREASE AGRICULTURAL PRODUCTION, CONSERVE NATURAL RESOURCES, AND ENHANCE ENVIRONMENT

Location: Coastal Plain Soil, Water and Plant Conservation Research

Title: Phosphorus dynamics and management in forage-based agroecosystem with cow-calf operation

Author
item Sigua, Gilbert

Submitted to: Agronomy for Sustainable Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 8, 2014
Publication Date: N/A

Interpretive Summary: Agroecosystems, including crop, pasture, and rangelands constitute over 70% of the continental United States and thereby play dominant roles in the management of the nation's watersheds and water resources. Pasturelands in the eastern United States of America are diverse as consequence of climatic conditions, previous land use, landscape position, dominant soil types, and management inputs. It is important to find a balance between the use of land and natural resources for agricultural production and society’s needs and values relating to the protection of the environment. Sustainable agriculture calls for natural resources to be managed in a way that ensures benefits are also available in the future. It takes into account the preservation of the overall balance and value of the natural capital stock and the need for agriculture to be viable and competitive. The nature of land management and land use are important issues within sustainable agriculture. A crucial key issue in order to minimize environmental impacts and enhance sustainability of beef cattle operations is to evaluate how different livestock management practices would affect the environment, including water quality, flora and fauna specie richness, and soil and landscape integrity. Contrary to early perception, forage-based animal production systems with grazing are not likely one of the major sources of non-point source phosphorus (P) pollution that are contributing to the degradation of water quality in lakes, reservoirs, rivers, and ground water aquifers, but perennially grass-covered pastures are associated with a number of environmental benefits. Continuous grass cover leads to the accumulation of soil organic matter, sequestering carbon in the soil and thereby reducing the potential carbon dioxide accumulation in the atmosphere. The increase in soil organic matter is also related to soil quality, with improvements in soil structure, aeration and microbial activity. Effective use and cycling of P is critical for pasture productivity and environmental stability. This will help to renew the focus on improving inorganic fertilizer efficiency in subtropical beef cattle systems, and maintaining a balance of P removed to P added to ensure healthy forage growth and minimize P runoff. New knowledge based on the whole-farm approach is desirable to identify pastureland at risk of degradation and to prescribe treatments or management practices needed to protect the natural resources while maintaining an economically and environmentally viable operation. Therefore, a better understanding of soil P dynamics, P use efficiency, and other crop nutrient changes in pastures with cow-calf management systems should allow us to better predict the least risk of P losses to adjacent surface water and ground water.

Technical Abstract: Forage-based animal production systems have been suggested as one of the major sources of non-point source of phosphorus (P) pollution that are contributing to the degradation of water quality in lakes, reservoirs, rivers, and ground water aquifers. Relatively little information exists regarding possible magnitudes of P losses from grazed pastures. Whether or not P losses from grazed pastures are significantly greater than background losses and how these losses are affected by soil, forage management, or stocking density are not well understood. This paper demonstrates the various effects of differing pasture fertility, animal behavior, and grazing management systems on the levels and changes of soil P in subtropical beef cattle pastures that will improve our understanding of P dynamics, cycling, and management in the agroecosystem. Continuous grass cover leads to the accumulation of soil organic matter. The increase in soil organic matter can be related to soil quality and soil health, with improvements in soil structure, aeration and microbial activity. Effective use and cycling of P is critical for pasture productivity and environmental stability. This will help to renew the focus on improving inorganic fertilizer efficiency in subtropical beef cattle systems, and maintaining a balance of P removed to P added to ensure healthy forage growth and minimize P runoff. Knowledge of the relationship of grazing intensity and the temporal and spatial accumulation of soil nutrients is necessary for developing improved grazing management, which could be both economically and environmentally discreet. Phosphorus dynamics in various agro-animal-ecosystems are continually evolving in response to changing management practices. A crucial key issue in order to minimize environmental impacts of P and enhance sustainability of beef cattle operations is to evaluate how different livestock management practices would affect the environment, including water quality, flora and fauna specie richness, and soil and landscape integrity.

Last Modified: 9/1/2014
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