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NONPOINT SOURCE POLLUTION AND TMDLS IN THREE GEOGRAPHICALLY DIVERSE WATERSHEDS

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

Citation:  Pp. 502-508 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:10.13031/2013.15606)
Authors:   J.S. Strock, D.J. Mulla, P.H. Gowda, J.D. Apland, K.W. Easter, and D. Bruening
Keywords:   TMDL, Nonpoint Source Pollution, Water Quality, Watershed

This project is an effort to evaluate nonpoint source pollution and Total Maximum Daily Loads (TMDLs) for three sub-watersheds located in the Cottonwood River Major Watershed (CRMW) in southwest Minnesota. Little effort has been given to determining the feasibility of attaining these TMDLs given a specific set of soil, landscape, climatic, management, and socio-economic characteristics in a watershed. Our approach involved a survey of existing farm management practices. The survey focused on basic farm characteristics, number and types of livestock, rates of fertilizer and manure applied, area of cultivated land and area used for manure application, timing of fertilizer and manure application, planting and harvest dates, crop yields, and pest management practices. A total of 6343 ha of farmland was inventoried in the study area for the 2002 crop season. Corn in rotation with soybean accounted for 93% of all crop land surveyed. Ten of the 40 farms surveyed in the study area were combination grain and livestock operations. Nitrogen applied from fertilizer and manure averaged 159 kg N/ha across all inventoried corn. Factoring in all appropriate credits there was an over-application of 25 kg N/ha across all inventoried corn within the study area. Results indicated that educational efforts to improve water quality can be achieved through better farm management practices such as managing timing and rate of fertilizer application.

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