Nitrogen management effects on spring wheat yield and protein concentration vary with seeding date and slope position

Efficient N fertilizer can improve economic returns and reduce environmental risk. This study evaluated effects of fertilizer rate, source, timing and placement combinations on spring wheat (Triticum aestivum L.) yield and protein concentration under varying environmental conditions created by differing slope position and seeding dates. Grain yield and protein responses to N management were evaluated for 3 yr at two locations near Brandon, MB, Canada. Grain yield was generally higher by up to 0.9 t ha−1 and protein lower by up to 20 g kg−1 on lower vs. upper slope positions. Grain yield was higher by up to 0.7 t ha−1 and protein concentration lower by 20 g kg−1 with early vs. late seeding. While grain yield and protein both usually increased with N application, by up to 25 and 20%, differences among fertilizer treatments were infrequent. In 2 site-years, grain yield was lower with fall- than spring-banded urea and the use of fall-banded controlled release urea (CRU) reduced N losses and led to yields intermediate between fall- and spring-banded urea. Where differences occurred among fertilizer treatments, yield was generally highest with spring side-banded urea. However, protein occasionally increased with use of CRU vs. urea fertilizer. Spring side-banded urea, although less costly than enhanced efficiency fertilizers or split N applications, produces both yield and protein concentrations as high or higher than a range of enhanced efficiency fertilizer products or split applications of N, and is a good N management option under environmental conditions in southwestern Manitoba.