Efficiency of Fall- Versus Spring-Applied Nitrogen for Winter Wheat
1966
Welch, L. F. | Johnson, P. E. | Pendleton, J. W. | Miller, L. B.
Winter wheat, Triticum aestivum L. ‘Monon’, was grown for 3 years on Cisne silt loam soil at Newton, Illinois. Fertilizer variables were O, 20, 40, and 60 pounds of nitrogen per acre applied in the fall and in the spring in factorial combination. Multiple regression equations for the regression of yield on nitrogen were calculated from yearly yields for each of the 3 years and from yields for the 3-year average. The equation for 1961–63 is: Y = 2123 + 14.287 Nf + 21.487 Nₛ − 0.028 Nf² − 0.066 Nₛ² − 0.142 NfNₛ Y is yield of wheat in pounds per acre, and Nf and Nₛ are pounds per acre of nitrogen added in the fall and in the spring. The largest yield increases from added nitrogen were 56, 23, and 117% in 1961, 1962, and 1963, respectively. A pound of nitrogen applied in the spring increased yields more than a pound of nitrogen applied in the fall. The relative efficiency of fall-applied nitrogen, with respect to spring-applied nitrogen, ranged from 0.55 to 0.97 for individual years and nitrogen rates. The relative efficiency of fall-applied nitrogen increased as the rate of nitrogen increased in 1962 and in 1963. For the 3-year yield average, the relative efficiency of fall applied nitrogen was 0.67 at all nitrogen rates. Weather data offered only a limited explanation for the variation in relative efficiency of fall-applied nitrogen from year to year.
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