Corn Grain Yield and Nutrient Response to Foliar Fertilizer Applied during Grain Fill

Recently there has been renewed interest in foliar fertilization of field crops, but little work with foliar application of nutrients on corn (Zea mays L.) during the grain filling period has been reported. This study was conducted to observe the effect of foliar fertilizer on corn grain yield, yield components, and nutrient content in the grain at harvest, while plants were subjected to moisture stress imposed after silking in one, two, or three successive stress periods. Experiments were conducted in the movable rain shelter facility at Ames, Ia., in 1976 and 1977. In this facility corn plants were grown in containers containing 100 liters of a Nicollet loam soil (an Aquic Hapludoll, fine-loamy mixed mesic). Foliar fertilizer was applied three times in the post-silking period with a pressurized hand sprayer. In 1976, foliar fertilizer application commenced 4 weeks after silking, and no significant effect of foliar fertilizer on yield, or yield components was measured. In 1977, foliar-fertilizer application commenced as early as 2 weeks after silking, and a significant, 6.4% yield reduction occurred in foliar-fertilizer treatments. This decrease occurred in both hybrids used and in all moisture-stress treatments. There was no evidence for an interaction between post-silking moisture stress and foliar-fertilizer application. In 1977, the effect of foliar fertilizer was to reduce mass/kernel in one hybrid, while in the other, neither mean mass/kernel nor kernels/plant were significantly reduced, but total grain yield was reduced. This difference was related to the number of days after silking when foliar fertilizer was first applied. Foliar fertilizer seemingly produced a stress on these plants, and the deleterious effect of this stress was expressed by the yield component being primarily determined at the time the stress occurred. Foliar fertilizer applications resulted in a significant increase in the percent N (10%) and in the percent P (4.7%) in the grain at harvest. There was, also, an increase in N yield (5.1%) in the grain despite a grain yield decrease in one hybrid.