Soybean seed treatment with chelated Ni and /or Si enhance nitrogen nutritional efficiency and mitigates micronutrient toxicity

The appropriate dose of Ni in chelated form applied in the treatment of soybean seeds grown in Entisols is not yet known, nor is it known whether Si would have an immediate effect that could mitigate the toxicity of Ni and the mechanisms involved. Therefore, this research was conducted to evaluate the effect of Ni doses applied via seed treatment on the modulation of physiological mechanisms that improve the initial growth of soybean plants, and whether Si acts as an attenuating agent that intensifies this modulation. To this end, two experiments were conducted in a greenhouse. In the first, Ni doses of 0, 1.75, 3.5, 5.25, and 7 g ha − 1 were applied via seed treatment; and in the second, the treatments consisted of control (0 g ha − 1 ) and Ni toxicity (7 g ha − 1 ) combined with Si (Ni+Si) (2 mmol L − 1 ) and without Si (Ni–Si). The evaluations were performed 30 days after plant emergence. Doses of 2.4 and 2.5 g ha − 1 of Ni in chelated form promoted greater Ni absorption by the plant, which resulted in less cellular electrolyte leakage and higher levels of phenols, chlorophyll, and photosynthetic efficiency. Consequently, N nutritional efficiency and plant growth were improved. The research provides new contributions to the better use of chelated Ni in soybean seed treatment and the feasibility of using Si to mitigate any micronutrient toxicity problems, strengthening the sustainable cultivation of this species.