Leaf application of nitrogen in different phenological stages in soybean and inoculation with Bradyrhizobium japonicum

A adubacao nitrogenada na cultura da soja, associada a inoculacao com a bacteria Bradyrhizobium japonicum e uma pratica comum na agricultura, no entanto, muito contestada. Objetivou-se neste estudo avaliar a resposta da soja a aplicacao foliar de N em diferentes estadios fenologicos e a aplicacao de inoculante com Bradyrhizobium japonicum. O experimento foi realizado em casa de vegetacao da Universidade do Estado de Mato Grosso, Alta Floresta-MT. Foi utilizado o delineamento experimental inteiramente casualizado em arranjo fatorial 4x2, sendo quatro epocas de aplicacao de nitrogenio (R1 - Inicio de floracao, R3 - Final da floracao, R5.1 - Graos perceptiveis ao tato e R5.3 - Maioria das vagens entre 25-50% de granacao) e presenca ou ausencia de Bradyrhizobium japonicum, com quatro repeticoes. Conclui-se que a aplicacao de nitrogenio foliar na cultura da soja no estagio R1 proporcionou aumento no acumulo de nitrogenio na parte aerea, no numero de vagens e de graos por planta. A presenca do inoculante proporcionou maior numero de vagens quando aplicou se N nas epocas R1 e R3, ja para a materia seca de parte aerea, o melhor resultado foi obtido, quando o N foi aplicado em R 5.3, na ausencia do inoculante.Palavras-chave: adubacao nitrogenada, fixacao biologica, inoculante. LEAF APPLICATION OF NITROGEN IN DIFFERENT PHENOLOGICAL STAGES IN SOYBEAN AND INOCULATION WITH Bradyrhizobium japonicum ABSTRACT:Nitrogen fertilization in soybean crop, associated with inoculation with a bacterium Bradyrhizobium japonicum is a common practice in agriculture, however, much contested. The objective of this study was to evaluate the response of soybeans to foliar application of N in different stages of phenology and the application of inoculant with the diazotrophic bacterium Bradyrhizobium japonicum. The experiment was carried out in a greenhouse at the State University of Mato Grosso, Alta Floresta-MT. The completely randomized experimental design was used in a 4x2 factorial arrangement, with 4 nitrogen application times (R1 - Beginning of flowering, R3 - Final flowering, R5.1 - Grains perceptible to touch and R5.3 - Most pods between 25 -50% granulation) and presence or absence of Bradyrhizobium japonicum, with 4 replicates. It was concluded that the application of leaf nitrogen in the non-stage soybean crop provided an increase in the accumulation of nitrogen in the aerial part, there is no number of pods and grains per plant. The presence of the inoculant provided a larger number of pods when applicable. N in the periods R1 and R3, and for the aerial part dry matter, the best result obtained when it was obtained in R 5.3, in the absence of the inoculant.Keywords: nitrogen fertilization, biological fixation, inoculant.