Corn Yield and Nitrogen Uptake in Monoculture and in Rotation with Soybean

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Abstract
Increasing crop N use efficiency and minimizing environmental risk require an accurate assessment of N taken up by the crop from different sources. We conducted this study to: (i) compare the grain yields of corn (Zea mays L.) in monoculture and in rotation with soybean [Glycine max (L.) Merr.]; (ii) determine the contributions of N from fertilizer, soil, and legume residue to corn in the rotation; and (iii) compare N fertilizer recovery in monoculture and in rotation. Two existing (>10 yr) irrigated corn‐soybean rotation areas in Kansas were used. The soils were Crete silt loam (fine, smectitic, mesic Pachic Argiustolls) and Eudora loam (coarse‐silty, mixed, superactive, mesic Fluventic Hapludolls). To trace the N through the rotation, 15N microplots (2.4 m2) were established int he corn. Microplots also were established in soybean to separately follow 15N from roots + soil and shoots to corn. Crop rotation and fertilizer addition increased corn yield at both sites for two growing seasons. Averaged for 2 yr, the amount of N needed in the continuous corn to achieve yield equal to that in rotation with no N added was equivalent to 144 kg N ha‐1 in the Crete silt loam and 155 kg N ha‐1 in the Eudora loam. Response to N was greater on the Eudora loam, probably because of textural and organic matter differences. In the Eudora soil, significantly higher amounts of soil N were taken up at harvest by corn in rotation, whereas, in the Crete soil, corn in monoculture took up significantly higher amounts of soil N. Corn plants recovered 3 kg N ha‐1 (3%) from soybean residue in the Eudora soil and 5 kg N ha‐1 (14%) in the Crete soil. The main value of legume residue appears to be long‐term maintenance of soil N to ensure adequate delivery to future crops.
Funding Information
  • U.S. Department of Agriculture

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