Side dressing nitrogen fertilization in soybean in association with inoculation

Abstract

The soybean is a crop that demands high levels of nitrogen (N) to express its productive potential. Supplemental fertilization with N can be a management strategy to increase the yield. This study aims to assess the effect of the N side dressing fertilization at the V4 stage of soybean, with and without inoculation, as well as its effects on the process of biological nitrogen fixation (BNF). The experimental design was randomized complete-block design with four replications in factorial scheme 2 × 5, where the seeds were either inoculated or not and received 5 doses of N: 0, 10, 20, 30, and 40 kg ha−1. Vegetative growth, nodulation, and yield components were evaluated. The stem diameter, plant height, and grain yield were not affected by inoculation, only by the N doses, with positive linear responses to the N supply. The leaf area responded positively to the seed inoculation and to the N supply. The node mass and viable node mass were not altered by seed inoculation or the supply of mineral N; and, until the dose of 40 kg ha−1, the node formation did not decrease. The number of pods per plant and the thousand-grain weight showed an interaction between inoculation and doses of N. The side dressing N fertilization at the V4 stage, until the dose of 40 kg ha−1, did not affect the vegetative growth and BNF, while it contributed to increase grain yield, even in the presence of inoculation.