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.

中文翻译：

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叶面氮作为刺激性施肥改变碳代谢、活性氧清除，并提高大豆-玉米轮作中的谷物产量

刺激性施肥是对其他施肥良好的作物补充施用低剂量的叶面肥，文献表明它可能会增加谷物产量。然而，这种潜在产量增加背后的生理机制尚不清楚。本研究调查了补充叶面氮 (N) 对大豆 [ Glycine max (L.) Merr.] 和玉米 ( Zea mays ) 营养、光合参数、抗氧化代谢、农艺参数和谷物产量的影响。我们测试了晚季低比率的存在与否（R ₃和 V ₁₀大豆和玉米）在主季大豆和淡季玉米中进行叶面施氮。虽然施氮对叶片养分浓度没有影响，但由于叶面施氮，两种作物的净光合速率、气孔导度、水分利用效率和羧化效率均增加。光合作用的改善是由于在灌浆前 Rubisco 活性和叶片中糖浓度的同时增加。叶面施氮还改善了抗氧化代谢，表明受精植物在其周期中受环境胁迫的影响较小。叶面施氮对代谢活动的改善不影响单株谷物，但增加了大豆和玉米的 100 粒质量和谷物产量。