NONPOINT SOURCE POLLUTION AND TMDLS IN THREE GEOGRAPHICALLY DIVERSE WATERSHEDS

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 attainingthese TMDLs given a specific set of soil, landscape, climatic, management, and socio-economiccharacteristics in a watershed. Our approach involved a survey of existing farm managementpractices. The survey focused on basic farm characteristics, number and types of livestock, ratesof 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 pestmanagement practices. A total of 6343 ha of farmland was inventoried in the study area for the2002 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 allinventoried corn within the study area. Results indicated that educational efforts to improvewater quality can be achieved through better farm management practices such as managingtiming and rate of fertilizer application.