Forms of application of nitrogen in different stages of the development of soybean culture / Formas da aplicação de nitrogênio em diferentes estádios do desenvolvimento da cultura da soja

Abstract

In Brazil, inoculation with Bradyrhizobium japonicum and B. elkanii strains is the main form of Nitrogen (N) supply to soybean, but there are reports of the use of mineral N as a complement to biological fixation. The objective was to evaluate the effect of different forms and times of N application on the development and yield of soybean. The treatments include a control without N application and in all other treatments 10 kg ha-1 of N was applied, altering the time (V2, V4, R1 or R2) and the application form, namely, at sowing, broadcast on topdressing or by leaf spraying. The application of N provided an increase in leaf area, dry mass of shoot, number of nodules and dry mass of nodules in treatments with application of N at sowing and N at V2 on topdressing. For plant height, the treatment with N at V2 by leaf spraying was superior compared to control. The weight of one thousand seeds was not affected by N application. For grain yield the treatments with application of N by leaf spraying in V2 and R1 were highlighted. The greatest increase in grain yield on soybean is reached with leaf spraying at V2 stage