Crop Sequence Effects on Response of Corn and Soil Inorganic Nitrogen to Fertilizer and Manure Nitrogen
- John A. Lory ,
- Gyles W. Randall and
- Michael P. Russelle
Fertilizer N and manure frequently are applied to corn (Zea mays L.) grown after alfalfa (Medicago sativa L.) at rates similar to those applied to continuous corn, although corn following alfalfa typically requires little additional N to attain maximum dry matter. Consequently, similar amounts of applied N may affect soil NO3 differently in rotational than in continuous corn. There is little information evaluating crop sequence effects on residual soil NO3 derived from fertilizer N and manure. In two 2-yr experiments at two locations in Minnesota, we evaluated the effect of crop sequence on response of corn grain dry matter, grain N, and stover N, and of soil inorganic N (NO3-N and NH4-N) to fertilizer N and dairy manure. Grain dry matter of first-year corn following alfalfa did not respond to applied N at Rosemount and typically was less responsive than continuous corn at Waseca. Crop sequence effects on soil NO3 response to manure and fertilizer N were similar. Preplant fertilizer N application of 157 kg ha−1 increased residual soil NO3-N the following spring an average of 45 kg ha−1 more in first-year corn following alfalfa than in continuous corn, except when excessive precipitation caused apparent high losses of applied N. Grain N content and soil NO3 responded similarly to fertilizer N in both second-year corn following alfalfa and continuous corn. Efforts to reduce the buildup and potential loss of soil NO3 in the corn portion of alfalfa-corn rotations should focus on reducing N application to first-year corn following alfalfa. These N applications have little agronomic value and can dramatically increase residual soil NO3.
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