Reductions in Nitrate Leaching Due to Management in Southwest Michigan.

Nitrate leaching was measured across a management intensity gradient in southwest Michigan. Treatments included four annual cropping systems on a corn-soybean-wheat rotation, two perennial crops, two successional treatments, and two forested treatments. Nitrate concentrations were measured in the leachate from each system using suction lysimeters from 1995-2007, and drainage was estimated using the System Approach to Land Use Sustainability (SALUS) Model. Systems were analyzed for total nitrate leaching throughout the entire 12 year period, as well as for leaching differences within the study period. Annual treatments leached the most nitrogen. The conventional annual cropping system leached more than all the other annual systems, while the organic leached the least. Of the perennial systems, the poplars lost very little nitrogen while the alfalfa showed higher losses. The successional systems showed very small losses of nitrogen, while the forested systems showed intermediate leaching values between the agricultural and successional treatments. Throughout the study period, there was strong year-to-year variation, most likely due to changes in precipitation patterns.