Influence of timing of nitrogen application on yield and nutrient uptake of winter wheat (Triticum aestivum L.)

Abstract

Replicated field experiments were conducted in 1981-82 and 1982-83 on a State loam soil to determine if split spring N applications have possible yield advantages over single N applications for soft red winter wheat (Triticum aestivum L.). Treatments included a single and various split applications of 89. 6 and 134. 4 kg N/ha. These were applied at specific stages of wheat development. A control treatment was included to determine the contribution of indigenous soil N to grain yield and nitrogen uptake.

Grain yields were increased by a split application of 134.4 kg N/ha (67.2 at G.S. 3.0 and 67.2 at G.S. 10.5) in 1982. No differences between grain yield for single and split N applications occurred in 1983. Yield levels averaged 6.25 and 7.21 Mg/ha for 1982 and 1983, respectively. Single N applications at G.S. 3.0 induced excessive tillering which was reflected in the higher number of tillers per m². Excessive tillering also resulted in increased lodging occurrence and reduced the harvest index. Increases in grain yield with split applications were attributed to greater photosynthetic efficiency in lower tiller densities of head-bearing tillers.

Split N applications also improved the nitrogen and phosphorous economy of winter wheat, which is shown by increases in the nitrogen and phosphorous harvest indices for split applications of 134.4 kg N/ha in 1983. This resulted from an increase uptake of these nutrients during post-floral grain development.

Analysis of the wheat tissue for N content at G.S. 5.0 indicates that tissue N levels reflect the amount of N applied. This suggest that tissue N analysis may be used to diagnose N deficiencies.