American Society of Agricultural and Biological Engineers



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Potential and Limitations of Management Practices to Reduce Nutrient Losses

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Pp. 074-079 in Total Maximum Daily Load (TMDL) Environmental Regulations–II Proceedings of the 8-12 November 2003 Conference (Albuquerque, New Mexico USA), Publication Date 8 November 2003.  .(doi:10.13031/2013.15540)
Authors:   J. L. Baker
Keywords:   water quality, nitrogen, phosphorus, best management practices, tillage, cropping, fertilizer, manure, hydrology, subsurface drainage, nonpoint pollution

Nonpoint source water quality concerns from nutrients lost from agricultural lands with surface runoff and subsurface drainage involve both human health and the integrity of aquatic ecosystems. Listing by states of impaired waters, relative to designated uses, illustrate that nutrient losses to both standing and flowing waters are a major cause of water quality problems. To solve these problems, the U.S. EPA is requiring states to develop practices/systems, and plans to implement them, through TMDLs. States are also being required to develop nutrient criteria for standing and flowing waters to be part of new standards that are protective of current and future uses. There are concerns as to whether the current suite of management practices will be adequate to meet the challenge.

In-field management practices involving nutrient (fertilizer and/or manure) applications, cropping, and tillage have real but somewhat limited potential to reduce nutrient losses. Optimum rate, method, and timing of nutrient applications all together may only have the potential for about a 20-25% reduction in losses over current practices. Depending on the degree of erosion, reduced tillage or no-till can significantly reduce nutrient losses associated with sediment, and alternate cropping including close-grown grains and/or sod-based rotations can reduce inputs and also reduce nutrient transport. When in-field practices are not adequate, constructed/reconstructed wetlands can be used to intercept nitrate-laden subsurface drainage and reduce transport via denitrification; and buffer/vegetated-filter strips can be used to reduce erosion, sediment transport, and the associated loss of nutrients. A key factor is the source area/wetland or strip area ratio.

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