Optimizing nitrogen fertilizer response by winter wheat and rye
Southwestern Alberta has been the traditional winter wheat production area in western Canada. In recent years, the adoption of a practical snow management system, which utilizes no-till seeding into standing stubble immediately after harvest of the previous crop, has resulted in an extension of this production area to include most of the western Canadian prairies. Winter rye is also adapted to the no-till production system developed for winter wheat. Most stubble fields are deficient in available soil nitrogen (N) with the result that N fertilizer is a major input cost in the production of no-till winter wheat and rye. This report summarizes the N response observed in 40 winter wheat and 20 winter rye trials representing a broad range of soil types and environments in western Canada. Nitrogen fertilizer did not have a significant influence on heading date, maturity, hectoliter weight or kernel size in most trials. Where a significant N response was detected, maximum differences were a one and two day delay in heading, a two and nine day delay in maturity, a three and three kg reduction in hectoliter weight, and a seven and nine mg reduction in seed size for wheat and rye, respectively. A significant N response was observed more frequently for height. In this instance, the response was not directional and increases up to 25 and eight cm and reductions to nine and nine cm were observed with increased N for wheat and rye, respectively. The Gompertz equation provided the most complete description of the relationship between protein concentration and total plant-available N. Predicted grain protein concentration from this equation explained 98 and 93 percent of the variability in actual grain protein concentration for wheat and rye, respectively. The N response curves for protein concentration were similar for winter wheat and rye. After an initial lag, protein concentration increased rapidly, and then tailed off at high N levels. An inverse polynomial function was employed to describe grain and protein yield response to N fertilizer. Predicted yields from these equations explained 96 and 88 percent of the variability in actual grain yield and 94 and 89 percent of the variability in actual protein yield for wheat and rye, respectively. Winter rye demonstrated a greater N use efficiency and yield potential than winter wheat. There was a large interdependence of N response and environmental conditions, especially moisture supply, in determining yield in these trials.
Soils and Crops Workshop