Submitted to: National Water Quality Monitoring Council
Publication Type: Abstract Only
Publication Acceptance Date: May 11, 2006
Publication Date: N/A
Technical Abstract:
Crop yield and nitrate nitrogen losses through subsurface drainage are affected by multiple climatic and management variables, however the interactive affect of these variables is not well understood. Simple equations that predict nitrate loading and crop yield as a function of important variables may improve our understanding of agricultural systems. Therefore, we developed multivariate polynomial regression equations to predict crop yield, nitrate concentration, drainage volume, and nitrate loading from a corn and soybean rotation in response to rainfall amount, N source, N rate, and timing of N application in northeastern Iowa. The regression equations described over 85% loading, 69% drainage, 60% yield, and 48% nitrate concentration variation. The regression equations were then used to analyze nitrate leaching and crop yield under a variety of N management and climate scenarios. The regression equations improve our understanding of variable interactions on nitrate leaching, offer a simple method to quantify potential N losses from Midwestern corn-soybean rotations, and are a step toward development of easy to use N management tools.
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