Yield of upland rice as affected by nitrogen application and seed inoculation with diazotrophic bacteria.

The use of nitrogen-fixing diazotrophic bactéria such as Azospirillum spp. could be an important alternative to reduce nitrogen fertilization in upland rice field. The objective of this study was to determine the effect of nitrogen application at topdressing and seed inoculation with strains of Azospirillum spp. on the plant biomass, foliar nutrient concentration, yield components, grain yield and nutrient concentration of grains in upland rice under a no-tillage system. The field experiments were conducted for two growing seasons 2015/2016 and 2016/2017 in the Cerrado Region of Brazil. The experimental design was a complete randomized block in a factorial 4x4 scheme with three replications. The treatments consisted of inoculated seeds of rice with peat containing the strains of Azospirillum spp. [Azospirillum brasilense 245, Hernaspirillum seropedicae Z94, commercial Azospirillum brasilense (Ab V5 and Ab V6 strains), and without Azospirillum] with four doses of N (0, 40, 80 and 120 kg há-1) applied as urea at topdressing. The use of diazotrophic bacteria in high level of soil organic matter did not increase yield componentes, grain yield and nutrients in the leaves and grains of upland rice. Increasing rates of N increased N, P, K, Ca, Mg, S, Cu and Mn in leaves; N, P, Ca, Cu and Fe in the grains, biomass, panicle per meter, grain per panicle and grain yield of upland rice. In this sense, the rate of 120 kg ha-1 of N provided the highest rice grain yield (4,413 kg ha-1)