Nickel application influences nitrogen concentration, yield, and grain quality of soybean

Nickel (Ni) is an essential element in nitrogen (N) metabolism. This study evaluated the effects of foliar fertilization with Ni on the grain yield (GY), yield components, N content, grain protein, and oil content of soybean [Glycine max (L.) Merr]. Two field experiments, each testing a different soybean cultivar, ‘BRS 284’ and ‘BRS 399RR’, were performed during the 2019–2020 and 2020–2021 growing seasons, in Londrina, Brazil. The experimental design was randomized blocks with three treatments (0, 60, and 120 g Ni ha⁻¹, using nickel chloride) and eight replications. Foliar application of Ni was performed by applying half of the rate at flowering and half during grain filling. The results showed that application of 60 and 120 g Ni increased the GY by 4.0% and 6.4% compared to the control in BRS 399RR in the first season. For BRS 284, no significant differences were observed in either season. N concentration in leaves improved by 7.1% and 7.8%, in the first and 18.5% and 14.0% in the second season under 60 and 120 g Ni rates, respectively, compared to control in BRS 284. For BRS 399RR, the leaf content of N increased 16.5% and 14.5% for both Ni rates compared to the control only in the first season. However, only in the second season, spraying 60 and 120 g Ni increased the N concentration in the grains by 7.9% and 22.4% for BRS 284 compared to the control. The effects of foliar Ni spray vary among soybean cultivars and dry periods, which influence N supply, use efficiency, and GY.