Effects of incremental N fertilization on grain yield and dry matter accumulation of six spring wheat (Triticum aestivum L.) cultivars in southern Manitoba.

A 3-yr study was conducted on three Orthic Black Chernozemic soils to determine the effects of incremental N fertilization on grain yield and dry matter accumulation and distribution of six spring wheat (Triticum aestivum L.) cultivars. Urea (46–0–0) was sidebanded at seeding in 40 kg N ha−1 increments from 0 to 240 kg ha−1 in the first year and from 0 to 200 kg ha−1 in the 2 subsequent years. Nitrogen fertilization increased the grain and straw yields of all cultivars in each experiment. The predominant factor affecting the N response and harvest index of each cultivar was available moisture. At two of the three sites, 91% of the interexperiment variability in mean maximum grain yield was explained by variation in root zone moisture at seeding. Mean maximum total dry matter varied by less than 12% among cultivars, but mean maximum grain yield varied by more than 30%. Three semidwarf cultivars, HY 320, Marshall and Solar, had consistently higher grain yield and grain yield response to N than Glenlea and K...