Foliar Applied Nitrogen Fertilizers in Spring Wheat.

Multiple foliar N fertilizer products are currently marketed as more efficient, advantageous N sources. Proposed benefits of foliar N products include increased N use efficiency (NUE), higher yields and, and savings in money, labor and time to wheat producers. The objective of this study was to evaluate the effect of foliar N fertilizer sources, rates and dilution ratios on spring wheat grain yield. Spring wheat is produced for its quality, represented by high grain protein content. Combining yield and protein into protein yield makes sense because N is vital to both yield and protein production. This study was initiated in the spring of 2012 at three locations: two dryland - at Western Triangle Agricultural Research Center (WTARC) (near Conrad, MT) and in a cooperating producer’s field (Jack Patton, Choteau County, MT), and one irrigated - at Western Agricultural Research Center (WARC) (near Corvallis, MT) using Choteau spring wheat. At planting, 90 kg N ha^-1 was applied as urea. At Feekes 5 growth stage, 56 kg N ha^-1was foliar applied utilizing an all-terrain vehicle (ATV)-mounted stream-bar equipped sprayer. Three foliar N sources – urea ammonium nitrate (UAN), liquid urea (LU), and high NRG-N (HNRGN) and three dilution ratios of fertilizer%/water% - 100/0, 66/33, and 33/66 - were evaluated. Preliminary results from the first year of study are reported here. When undiluted N products were used, the highest grain yields were obtained with HNRGN at all 3 sites. There were no significantly difference differences in yield, protein or protein yield associated with product to water ratio at any of three sites. In general, the highest yield, protein and protein yield were achieved with the ratio of 33%/66%, followed by 100%/0%, and the lowest – at the ratio of 66%/33% at all three sites. Highest grain yields were obtained with HNRGN at all 3 sites, independent of the product to water ratio. At dryland sites grain yields increased significantly as follws: UAN<LU<HNRGN. At the irrigated site, yields obtained with UAN and HNRGN were comparable, while LU resulted in lower yields. Grain protein was maximized with LU at the irrigated location; lower protein was obtained with UAN and HNRGN. At WTARC, similar trend was observed, but the differences were not significant. At Patton, grain protein increased as LU>HNRGN>UAN. At dryland sites, HNRGN resulted in a combination of highest protein yield. At the irrigated site, the same trend was observed, but the differences were not significant. The lowest protein yield at the dryland sites was achieved with UAN, and with LU - at the irrigated site. Due to LU and HNRGN’s lower corrosiveness compared to UAN, even when applied undiluted, LU and HNRGN may be a better choice among the three foliar products evaluated. The cost of HNRGN at the time of application was approximately 25% higher than cost of LU, and almost 30% higher than cost of UAN.