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

Irvine, R. B., Lafond, G. P., May, W. E., Kutcher, H. R. and Holzapfel, C. B. 2010. Alternative nitrogen management options for winter wheat on the eastern prairies of western Canada. Can. J. Plant Sci. 90: 471-478. 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 I, 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.