Nitrogen supplementation improves yield and quality of soybean seeds
Nitrogen use in soybeans is still not fully taken advantage of. Increased use of nitrogen fertilizer couldnot only increase agricultural productivity, but also strengthen food security in the context of the increasing global need for food. The objective of this study was to evaluate the performance and seed quality of soybeans supplemented with nitrogen. The research was carried out in the municipality of Los Cedrales, Alto Paraná, Paraguay. The trial was conducted in an experimental design of randomized blocks, organized in factorial scheme 2 (genotypes) x 4 (fertilization management). The evaluated genotypes were cultivar DM 5958 RSF Ipro and cultivar 6410 Ipro, both registered, protected and indicated for cultivation in the southern region of Brazil and in Paraguay. Nitrogen fertilization treatments were defined considering the ease of application of doses at soybean development stages. In 10 plants per experimental unit, the following variables were determined: plant height, number of nodes, pods and seeds per plant, and the weight of one thousand seeds. The grain yield (GY, kg ha-1) was determined by harvesting the useful area of each experimental unit, corrected to 13% humidity. The physiological quality of seeds was evaluated through the following variables: germination and vigor of seeds and emergence of seedlings in beds. Nitrogen supplementation significantly increased the number of nodes, the weight of a thousand seeds and the number of soybean pods. Compared to no N application (0R2/0R5), treatments with application of 120 kg ha¹ of N in R2 (120R2/0R5); and 60 kg ha¹ of N in R2 and R5 (60R2/60R5) of soybeans, caused increases in seed productivity of 7 and 8%, and in the physiological quality of seeds with increases of up to 7 and 5% in vigor and seedling emergence, respectively. Based on soil and climate conditions, genotypes, management, and analyses performed, the split application of 120 kg ha-1 of N between stages R2 and R5 resulted in higher productivity and greater physiological quality of the soybean seeds.