Effect of Fertilization Method and Tillage on Nitrogen-15 Recovery by Corn
- D. R. Timmons and
- R. M. Cruse
Fertilizer N utilization by corn (Zea mays L.) is influenced by different fertilizer management and tillage systems. A study was conducted in central Iowa during two consecutive years to evaluate the uptake and recovery of labeled N for continuous corn grown in two tillage systems with two fertilization methods. Tillage systems were fall moldboard-plow and ridge-till. Labeled N (5% 15N) as 28% urea-ammonium nitrate solution (UAN) was either surface-applied in the fall before any primary tillage or banded (knifed-in) between rows at 224 kg N ha−1 just before planting. Depending on tillage and fertilization method, corn grain yields ranged from 1.3 to 7.3 Mg ha−1 which were below normal due to adverse weather conditions during the two growing seasons. The percent of plant N derived from labeled N (Nr) in the sixth leaf (50% silk) and in mature grain, stover, and whole plants was significantly lower for fall surfaceapplied 15N than for spring banded 15N. For mature whole plants, Nr ranged from 9 to 59% and averaged 53% for spring banded and 17% for fall surface-applied 15N. Labeled N recovery by mature corn grain was affected by fertilization method and growing season and ranged from 1 to 25% during the 2-yr period. Labeled N recovery by mature whole plants ranged from 2 to 41% and averaged four times greater for spring banded than for fall surface-applied 15N. About 1 yr after application, an average of 20% of the 15N remained in the soil profile; and 95% of the residual 15N was found in the organic N pool. Compared with spring banded N, fall surface-applied N was extremely inefficient for both tillage systems.
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