Nutrient losses from row-crop land can cause nonpoint source water quality problems and “impaired waters.” Nitrogen (N) losses due to nitrate (NO3) leaching cause drinking water problems and possibly increase hypoxia (low oxygen) problems in the Gulf of Mexico. Phosphorus (P) losses can cause eutrophication problems in surface waters (lakes, streams, and reservoirs) in Iowa where algal blooms decrease oxygen, kill fish, and result in murky and bad tasting water. The U.S. EPA and the Iowa Department of Natural Resources are developing nutrient criteria/standards and implementation plans to address TMDL’s (Total Maximum Daily Load) and to improve the quality of impaired waters. These plans need to be based on sound information. To address the need for information about water quality impacts from the use of swine manure as a source of nutrients (N and P), a field study was funded by the Leopold Center for Sustainable Agriculture in 1999. Properly managed, swine manure can supply N and P needed by corn and soybeans. This study is being conducted at the Northeast Research Farm on 36 one-acre plots that are instrumented to monitor subsurface drainage for continuous water quality assessment.