Foliar nitrogen as stimulant fertilization alters carbon metabolism, reactive oxygen species scavenging, and enhances grain yield in a soybean–maize rotation

Abstract

Stimulant fertilization isthe supplementary application of low doses of foliar fertilizers to otherwise well-fertilized crops, and literature suggests that it may increase grain yield. However, the physiological mechanisms behind this potential yield increase are not well understood. This study investigated the effect of supplementary foliar nitrogen (N) in soybean [Glycine max (L.) Merr.] and maize (Zea mays) nutrition, photosynthetic parameters, antioxidant metabolism, agronomic parameters, and grain yield. We tested the presence or absence of low rates of late season (R3 and V10 of soybean and maize, respectively) foliar N fertilization in a main season soybean followed by an off-season maize. While there were no effects of N application on leaf nutrient concentration, the net photosynthetic rate, stomatal conductance, water use efficiency, and carboxylation efficiency increased due to foliar N fertilization in both crops. The improvement in photosynthesis occurred due to a concomitant increase in Rubisco activity and in the concentration of sugar in the leaves prior to grain filling. Foliar N fertilization also improved antioxidant metabolism, suggesting that fertilized plants were less affected by environmental stresses during their cycle. The improvement in the metabolic activity due to foliar N did not affect grains per plant but increased a hundred grain mass and grain yield of both soybean and maize. Our results suggest that foliar N applied as stimulant fertilizer is a promising strategy to increase yield of maize and soybean crops.