Effect of nitrogen fertilization associated with inoculation of Azospirillum brasilense and Herbaspirillum seropedicae on corn

The growing interest in the use of inoculants with diazotrophic bacteria that promote plant growth, providing increase in crop productivity, occurs because of the high costs of chemical fertilizers and the concern about environmental quality. Given the above, this study aimed to evaluate, in field conditions, the effect of nitrogen fertilization and inoculation with Azospirillum brasilense and Herbaspirillum seropedicae on the productivity, phytotechnical parameters and nutritional state of corn. The experiment was set in a randomized block design, with nine treatments and six replicates: Control without N and without inoculation; A. brasilense inoculation without N; H. seropedicae inoculation without N; 30 kg ha-1 of N at the sowing; A. brasilense + 30 kg ha-1 of N at the sowing; H. seropedicae + 30 kg ha-1 of N at the sowing; 30 kg ha-1 of N at the sowing + 90 kg ha-1 of N in covering; A. brasilense + 30 kg ha-1 of N at the sowing + 90 kg ha-1 of N in covering; and H. seropedicae + 30 kg ha-1 of N at the sowing + 90 kg ha-1 of N in covering. The evaluated parameters were: plant height, stem diameter, ear insertion height, ear weight, ear length, number of grain rows per ear, number of grains per ear, ear base diameter, weight of 1,000 grains, shoot dry weight, yield, chlorophyll content, leaf nutrient content and grain nutrient content. The nitrogen fertilization associated with inoculation of A. brasilense and H. seropedicae positively influenced ear weight, ear diameter, number of grains per ear, shoot dry weight, yield and chlorophyll content of corn plants. The contents of N, P, K and Zn in corn leaves increased with nitrogen fertilization and inoculation with A. brasilense and H. seropedicae. The inoculation with A. brasilense without nitrogen fertilization promoted higher accumulations of N, K, Ca and Mg in grains compared with the treatments inoculated with A. brasilense and H. seropedicae and fertilized with 30 and 120 kg ha-1 of N. The inoculation with A. brasilense or H. seropedicae associated with nitrogen fertilization may lead to a reduction in the use of synthetic nitrogen fertilizers in corn cultivation.   Key words: Zea mays L., nitrogen, diazotrophic bacteria.