OOS 29-2 - Managing agricultural P to protect water quality - obvious priorities and obscure necessities

Wednesday, August 10, 2011: 1:50 PM
12A, Austin Convention Center
Michael Castellano, Iowa State University, Peter Kleinman, Pasture Systems and Watershed Management Research Unit, USDA Agricultural Research Service, University Park, PA and Andrew N. Sharpley, Dept. Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR
Background/Question/Methods . Current concerns over agriculture's contribution to cultural eutrophication stem from a variety of factors.  The specialization and intensification of our farming systems, an economically-driven adaptation an adaptation to urbanization and dietary shift, has driven regional and local surpluses of phosphorus (P) that are strongly tied to livestock production. 

Results/Conclusions . There are promising options for reducing P surpluses at the farm gate, such as diet modifications, nutrient management planning, and precision applications.  However, the systemic nature of nutrient flows limits the options that farmers possess to voluntarily achieve these balances.  In the mid-term, substantial changes to off-farm markets and infrastructure are needed for manures.  On the farm, P management options are highly site specific, demanding an ability to prioritize cost-effective management practices that conserve P from barn to field. In some cases, practices to minimize P runoff conflict with other conservation priorities. Even low-input and low-intensity forms of agriculture, such as grazing systems, can yield significant environmental losses of P to water.  As such, water quality protection requires a concerted effort that extends beyond the expectations of the most conscientious farmers and certainly beyond the grasp of most consumers.  Developing watershed strategies that aggregate management above the farm level and that link demand for clean water and cheap food is a process that requires profound societal commitment.

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