Soybean Yield and Nutritional Status Response to Nitrogen Sources and Rates of Foliar Fertilization

The response of soybean [Glycine max (L.) Merr.] to foliar N application during pod formation has been inconsistent. The objective of this study over three growing seasons was to evaluate the eff ects of foliar N sources and rates of application on yield, nutritional status, and yield components of soybean. The treatments consisted of five sources [NO3NH4, CaNO3, KNO3, urea[CO(NH2)(2)], and (NH4)(2)SO4], two N rates (5 and 10 kg N ha(-1)), applied at the beginning pod growth stage, and a control (no-N fertilization). Foliar N generally increased the seed yield, irrespective of the N source and analysis pooled over three growing seasons showed an average seed yield increase of 5.0% (211 kg ha(-1)) and 6.1% (259 kg ha(-1)) for the 5 and 10 kg N ha(-1) over control, respectively. Neither N rate nor source aff ected seed size, protein, oil, and nutritional status of leaves or seed. Nitrogen rate aff ected N use effi ciency, but results varied with N sources. These data suggest that foliar N application may increase yield of soybean under certain environmental conditions.