Managing nitrogen for water quality-lessons from Management Systems Evaluation Area

The! Management Systems Evaluation Area (MSEA) project was initiated in 199 0 to evaluate existing and develop new N management technologies to reduce the potential adverse impacts of agricultural practices on surface and grou nd water quality, Field research sites were established in nine Midwestern states. Results from MSEA research showed that nitrate leaching was greatly reduced by changing from furrow to sprinkler irrigation. At least 95% of t he nitrate N percolating through tiled soils was intercepted and discharged into surface waters. Computer models indicated that routing tile discharge through wetlands would greatly reduce the nitrate load. Nitrate losses als o were reduced by establishing controlled water tables using drainage lines for subirrigation. Preplant and presidedress soil nitrate tests were effec tive in determining proper N fertilizer rates and reducing nitrate losses. Banding ammoniated fertilizers slowed nitrification rates and nitrate leach ing, especially if soil over the bands was packed, A major new technology w as proof that crop greenness can be used to monitor crop N sufficiency, and that N deficiencies after the V8 stage can be corrected by sidedressing or fertigation (reactive N management). Inexpensive sensors or aerial photogr aphs can be used to assess crop greenness. Using Global Positioning Systems (GPS), N-deficient areas of the field ran he managed differently from the remainder of the field. These results point to the need to develop site-spe cific or precision farming systems to control nitrate losses to water resou rces and reduce the impart of natural variability in both soils and weather .