Feasibility of applying all nitrogen and phosphorus requirements at planting of no-till winter wheat

Abstract

The recent advances in no-till seeding technology are providing new N management options for crop production on the prairies. The objectives of this study were to evaluate the potential interaction between P and N fertilizer on winter wheat production in a one-pass seeding and fertilizing system and to determine the feasibility of side-banding all N requirements using urea or anhydrous ammonia at planting as compared with the current practice of broadcasting ammonium nitrate early in the spring. Three forms of N fertilizer (urea, anhydrous ammonia, ammonium nitrate), three rates of N (50, 75 and 100 kg ha–1) and three rates of P (0, 9 and 17 kg P ha–1) were investigated. Urea and anhydrous ammonia were applied during the seeding operation, whereas ammonium nitrate was broadcast the following spring. Applying P fertilizer to the side and below the seed at planting with rates > 9 kg Pha–1 increased grain yield in 3 out of 6 site-years when ammonium nitrate was broadcast early in the spring. The positive yield response to P corresponded to soil test levels of 24 kg P ha–1. With soil test levels greater than 34 kg P ha–1, grain yield response to P fertilizer was not observed. When urea was banded at planting, together with P fertilizer, the yield increases with the increased P rates was shown only in 1 out of 6 site-years. At 5 of th e 6 site-years, grain protein concentration was not affected by P fertilizer; while for 1 site-year, the high rate of P fertilization decreased grain protein concentration. Responses of total grain N and P yields to P fertilization were parallel to the corresponding responses of P fertilization to grain yield, and were rarely associated with N or P concentrations in the grain. Applying N fertilizer at rates of 50 to 100 kg N ha–1 increased winter wheat grain yields by 3 to 8% in 3 out of 6 site-years. The high N rates increased grain protein concentrations in all 6 site-years. Grain protein concentration was 6% greater with N fertilizer applied as ammonium nitrate in early spring than when banding urea or anhydrous ammonia at planting. More consistent improvements in grain yield and grain protein concentration were obtained when the N fertilizer was applied as ammonium nitrate in the spring. Further research is required to determine the benefits of applying some of the crop’s N fertilizer requirements at planting, to reduce the risks of N stresses when the spring application is delayed because of adverse weather or soil conditions. Key words: Ammonium nitrate, anhydrous ammonia, grain yield, nitrogen timing, phosphorus, protein, urea