Foliar Applied Nitrogen Fertilizers In Spring Wheat.

Montana is traditionally recognized worldwide for production of high quality wheat. Spring wheat continues to be the key cereal crop for the state of Montana. While nitrogen (N) is considered the most common nutrient limiting yield of wheat and other cereal crops in Montana, N use efficiency (NUE) is estimated to be only about 33%. The most practical and ethical solution to meet crops’ nutrient needs is establishing more efficient ways to fertilize the crops. The scientific community and crop producers alike are debating whether foliar applied N fertilizers are more efficient compared to the soil applied fertilizers. There is a need to evaluated foliar N fertilizer products currently marketed as more efficient, advantageous N sources. Manufacturers claim that foliar feeding increases NUE, saves money, labor and time to wheat producers. Limited scientific research on foliar fertilizers and contradicting results emphasize the necessity to further investigate the efficacy of foliar N products and provide up-to-date unbiased information to wheat growers. The objectives of this study were: 1. To compare the efficacy of foliar N fertilizers (urea ammonium nitrate (UAN), liquid urea, and High NRG-N) applied to spring wheat, and 2. To determine the optimum dilution ratio of foliar fertilizers and the threshold at which spring wheat grain yield is reduced due to leaf burn. Three experiments were established: two dryland - at Western Triangle Agricultural Research Center (WTARC) (near Conrad, MT) and in a cooperating producer’s field (Lindsey Martin, Teton County, MT), and one irrigated – at Western Agricultural Research Center (WARC) (near Corvallis, MT) using Choteau spring wheat. At planting, 80 lb N ac^-1 were applied as urea. At growth stage Feekes 5, topdress N will be foliar applied utilizing an ATV-mounted sprayer using three N sources – UAN, liquid urea, and high NRG-N. Topdress was of 50 lb N ac^-1 at and 3 dilution ratios 100/0, 66/33, and 33/66 (fertilizer %/water %) were evaluated. Grain yield, grain protein content, N uptake and NUE were assessed using statistical procedures. This study aims to determine if any of the three evaluated foliar N fertilizers – UAN, liquid urea, and high NRG-N – have any advantage such as grain yield increase, enhanced protein content, increased NUE, or minimized leaf burn when applied to wheat crop canopy midseason. This will allow us to make recommendations regarding the optimum rate and efficacy of foliar fertilization in spring wheat.