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In summary, the effect of Ni on the plants was positive and the extent of this effect was controlled by genotype-environment interaction. Nickel supply also positively affected photosynthesis in the genotypes, never causing detrimental effects, except for the eu3-a mutant, which due to the absence of ureolytic activity accumulated excess urea in leaves and had reduced yield. Yield gains of up to 2.9 g per plant in greenhouse and up to 1,502 kg ha −1 in field conditions were associated with a promoted N metabolism, namely, leaf N concentration, ammonia, ureides, urea, and urease activity, which separated the genotypes into groups of Ni responsiveness. Nickel fertilization resulted in greater grain yield in some genotypes, indicating the hidden deficiency of Ni in both conditions. Plants were evaluated for yield, Ni and N concentration, photosynthesis, and N metabolism. For this, we used 15 soybean genotypes and two soybean isogenic lines (urease positive, Eu3 urease activity-null, eu3-a, formerly eu3-e1). To verify this hypothesis, two simultaneous experiments were carried out, under greenhouse and field conditions, with Ni supply of 0.0 or 0.5 mg of Ni kg −1 of soil. Thus, we hypothesized that Ni fertilization in soybean genotypes results in a better nitrogen physiological function and in higher grain production due to the hidden deficiency of this micronutrient. Soybean, a crop cultivated on soils poor in extractable Ni, has a high dependence on biological nitrogen fixation (BNF), in which Ni plays a key role. However, to date there are no records of Ni deficiency for annual species cultivated under field conditions, possibly because of the non-appearance of obvious and distinctive symptoms, i.e., a hidden (or latent) deficiency. Nickel (Ni)-a component of urease and hydrogenase-was the latest nutrient to be recognized as an essential element for plants. 4Laboratory of Plant Nutrition and Crop Physiology, Department of Crop Science, Faculty of Agriculture, University of Göttingen, Göttingen, Germany.3CropSolutions Agricultural Research Center, São Gabriel do Oeste, Brazil.