Effect of Nitrogen Sources, Rates, and Application Time On Spring Wheat Yield and Grain Protein.

Nitrogen (N) is considered the most common nutrient limiting yield of spring wheat and other cereal crops in Montana. Wheat production represents almost 25% of total Montana’s agricultural revenue. Nitrogen is a primary constituent of proteins; thus, N nutrition directly and radically impacts spring wheat production profitability. The major objective of this study is to determine the most efficient N fertilizer source, rate, and application time combination for optimizing Montana spring wheat yield while maximizing grain protein. Three dryland experiments will be established: one at Western Triangle Agricultural Research Center near Conrad, MT, and two at cooperating producers’ fields (at Knees, Chouteau County, MT and at Valier, Pondera County, MT) using Choteau spring wheat variety. A combination of 4 preplant N rates (0, 40, 80, and 120 lbs N ac), 3 topdress N rates (0, 40, and 80 lb N ac), 2 topdress N fertilizer sources (granual – urea, 46-0-0,  and liquid – urea ammonium nitrate (UAN) , 28-0-0), and 2 topdress application times (before flowering and after flowering) will be evaluated. Urea will be manually broadcasted and UAN will be applied as a foliar spray using backpack sprayers. Total yield and total crop N uptake will be determined at crop maturity, and grain yield and protein content determined after ripening. There is a need for locally-based field studies that would provide up-to-date, scientifically sound and unbiased information that would help Montana grain producers to make more educated nutrient management decisions. This study will assist crop producers by providing such information based on systematic and comprehensive evaluation of risks and benefits associated with various fertilization practices.