| Autor: |
Hesterman, O. B., Russelle, M. P., Sheaffer, C. C., Heichel, G. H. |
| Zdroj: |
Agronomy Journal; July 1987, Vol. 79 Issue: 4 p726-731, 6p |
| Abstrakt: |
Legume‐corn (Zea maysL.) rotations are common throughout the U.S. Corn Belt, but little information is available about the efficiency of legume residue N utilization, or about fertilizer‐N use efficiency in different cropping sequences. Our objective was to determine the contribution of N from soil, fertilizer, and legume residues for six legume‐corn sequences. The effect of applied fertilizer N rate was also examined. Field studies were conducted on a Udorthentic Haploboroll and a Typic Hapludoll. First‐phase (Year 1) rotation components included alfalfa (Medicago sativaL.), corn, soybean [Glycine maxL. (Merr.)], or fallow. Nitrogen–15‐depleted (NH4)2SO4was applied to second‐phase (Year 2) corn. Fertilizer‐N use efficiency for second‐phase corn was 51% for the whole plant and 36% for grain, with no effect of first‐phase treatment. Average use efficiency of legume‐N (uptake of legume‐N/legume‐N incorporated) was 43% for the whole corn plant and 30% for grain. Second‐phase corn derived a greater proportion of its N from residue of alfalfa (36%) than soybean (12%). When the rate of N applied to corn was increased from 56 to 168 kg N ha−1, the proportion of N derived from legume residue decreased from 44 to 19% in whole corn plants and from 57 to 23% in grain. Results suggest that the N credit commonly attributed to legumes in crop rotation may be inflated by as much as 132%. |
| Databáze: |
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