Alternative nitrogen management options for winter wheat on the eastern prairies of western Canada

Abstract

. 2010. Alternative nitrogen management options for winter wheat on the eastern prairies of western Canada. Can. J. Plant Sci. 90: 471Á478. Since fertilizer-grade ammonium nitrate is no longer available for general use in Canada, there is much discussion about the best management practices to minimize nitrogen (N) loss when fertilizing winter wheat. In two separate trials we compared several fall and spring N management options with the standard practice of spring-applied ammonium nitrate. In Study 1, the use of a coulter in fall or spring reduced seed yields, even when ammonium nitrate (AN) was broadcast in the spring, indicating crop damage. Spring broadcast applications of urea and urea ammonium nitrate (UAN) produced yields equivalent to spring broadcast AN. Urea applied at the time of planting produced seed yields relative to spring application of AN. The late fall UAN treatment had lower yields than when this product was applied in the spring. Protein levels varied among site-years, but were generally lower than the marketing target of 115 g kg (1 , which indicates less than optimal N levels or N uptake. In both studies, late fall surface banded UAN was inferior to other products and timings. In Study 2, seed yield and protein content were similar for all forms of urea placed at seeding, and these were similar to spring broadcast AN. We also found that under the relatively low fall and spring moisture conditions encountered in Study 2 protected N sources did not increase N use efficiency.

Influence of N fertilization method on weed growth, grain yield and grain protein concentration in no-till winter wheat

“…However, winter survival was unaffected in other studies (Middleton et al 2004;Blackshaw 2004;Irvine et al 2010). Variation in the response to fall N fertilization may be due to differences in cold-tolerance among cultivars and in severity of cold temperature stress.…”

“…However, in studies comparing urea and PCU applied at seeding for winter wheat, grain yield and protein concentration were similar as long as there was sufficient separation between the seed and applied urea (Middleton et al 2004;McKenzie et al 2007;Irvine et al 2010). The similar efficacy of PCU and urea in these studies was possibly due to relatively dry conditions and negligible over-winter N loss.…”

“…On average, crop plant density was 2.5% lower for fall band application than spring broadcast application, but this effect depended on site-year: crop plant density was 13% lower for fall band application than spring broadcast application at Dry-06 and Irr-05, but unaffected by method of application at the remaining site-years (data not presented). Previous studies also indicate an inconsistent effect of fall N application on plant stand: fall N application reduced plant stand in some studies (Grant et al 1984;Gusta et al 1999), but not others (Blackshaw 2004;Middleton et al 2004;Irvine et al 2010).…”

“…In more humid regions of the prairies, spring broadcast ammonium nitrate was generally more effective than fall N application due to the greater risk of over-winter N loss (Grant et al 1985;Fowler and Brydon 1989a, b;Campbell et al 1991;Johnston and Fowler 1991a, b). For spring broadcast application, urea was less effective than ammonium nitrate in three of nine trials in a study by Fowler and Brydon (1989a), but equally effective in other studies (Campbell et al 1991;Middleton et al 2004;McKenzie et al 2007;Irvine et al 2010), despite the potential for volatilization losses of ammonia from broadcast urea (Harrison and Webb 2001).…”

“…A high rate of fertilizer N and possibly late N application may be required to reliably achieve this protein level, particularly in humid regions (Fowler et al 1989;Bly and Woodard 2003;Irvine et al 2010).…”