Biometric, Nutritional and Productive Responses in Soybean Crops Induced by Foliar Application of Amino Acids

Amino acids play diverse roles in regulating plant metabolism and several metabolic processes essential for plant development, which is why they are widely used in plant biostimulation. Based on the hypothesis that amino acids improve productive performance, biometric variables, and nutrient content in plants, this study aimed to evaluate the effect of foliar application of individual amino acids on the development, productivity, and nutrition of soybean crops. The experiment was conducted under field conditions in a dystrophic Red Latosol using a no-till system. A randomized block design was used with 20 treatments and four replications. The treatments consisted of the foliar application of isolated amino acids: aspartic acid, arginine, cysteine, cystine, citrulline, phenylalanine, glycine, glutamine, isoleucine, leucine, lysine, methionine, ornithine, proline, taurine, tyrosine, threonine, tryptophan, and valine, applied at a rate of 20 g ha⁻¹ at two phenological stages of soybean (V4 + R1). Biometric variables (plant height, stem diameter, number of internodes, plant height, number of leaves, number of branches, and number of pods), nutritional variables (N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn), and productive variables (100-seed weight and grain yield) were evaluated. The amino acids promoted increases in soybean grain yield.