Submitted to: Clean Water Clean Environment 21st Century Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/5/1995
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Alternate farming practices are needed to decrease their negative impact on groundwater quality. Field studies were initiated in northeast Iowa during the fall of 1992, to evaluate effects of nine alternative N, tillage, and crop management strategies on N loss to the shallow groundwater. Use of the late-spring nitrate test (LSNT) and differential N fertilization rates based on those data resulted in lower nitrate concentrations in tile water beneath no-till and chisel plow treatments than with manure application or preplant N at rates of 100 lb/ac. The alfalfa and narrow-strip crop plots had the lowest nitrate concentrations (less than 10 mg/L). Corn following soybean on plots fertilized with swine manure had an average yield that was 1 bu/ac higher than with the LSNT, but because of the difficulty in applying the intended amount of N with manure, nitrate concentrations in the tile water were much higher. When averaged for the two years, no-till yield was slightly lower, but for both tillage practices, use of the LSNT resulted in equal or better yields than either preplant fertilization or application of swine manure.