Optimum Nitrogen Fertilizer Management Strategies for High-Yielding Spring Wheat in Manitoba.

Manitoba producers are growing varieties of hard red spring wheat with very high yield potential, which has brought out challenges in our nitrogen management strategies. Current provincial guidelines are based on much lower yielding varieties and these recommendations (2.5 lbs. N bu^-1 for milling quality wheat) create a large financial, agronomic and environmental risk for these high yielding varieties.

Field studies at 4 locations in each of 2016-17 focused on evaluating a number of nitrogen rate, timing and source combinations.

In 2016, the maximum N rate to significantly increase grain yield was 122 kg N ha^-1 at 3 sites. The maximum N rate to significantly increase protein content was 122 kg N ha^-1 at Carman and Melita and 190 kg N ha^-1 at Brunkild. Increasing N rate had no effect on grain yield or protein content at the 4^th site with high residual soil N.

Split N applications at tillering and flag leaf increased protein at 1 of the 4 sites, but did not affect yield. Post anthesis applications of N increased grain protein content at all sites, compared to equivalent rates of N at planting, however yield was reduced at 2 of the 4 sites.

ESN:Urea blends produced grain yields and protein content that were similar to those for conventional urea when applied at planting. Urea solution significantly increased protein content over UAN when applied post anthesis but yields for the two sources were similar.