ABSTRACT. Nitrogen is available in insufficient quantities in Brazilian soils, and is the nutrient that raises the most cost of production of maize. Nowadays there is a more interest in the use of alternative nitrogen sources, such as biological nitrogen fixation, to supply plant demand. Among the most used bacteria in association with grasses is Azospirillum brasilense. In this way this study aimed to establish a relationship between the genetic bases of corn and the forms of A. brasilense application and the effects on the plant morphological components, grain yield, and relative nitrogen contribution. Experiments were conducted during the 2013/14 and 2014/15 crop seasons. The experiments included two single hybrids, two double hybrids, and two triple hybrids inoculated with A. brasilense via seed treatment; foliar application during phenological stages V2, V2 + V4, and V4; and a control treatment without bacteria. The response varied with the hybrid and the year. In the 2013/14 crop, a significant difference was observed in the grain yield for the single hybrid AG9045 inoculated with A. brasilense via seed and foliar application in V2. In the 2014/15 crop, inoculation with A. brasilense via seed application resulted in significant increases in the grain yield for the triple hybrid BG7051. Foliar application of A. brasilense is an efficient alternative for the improvement of plant morphological traits, and inoculation via seed and with foliar application in V2 increases the relative contribution of N.

O nitrogênio (N) é o nutriente que mais limita a produtividade da cultura do milho. Dessa forma, o objetivo deste trabalho foi avaliar métodos de inoculação de Azospirillum brasilense para suprir em parte o nitrogênio requerido pela cultura. O experimento foi conduzido em Guarapuava, PR, Brasil, no ano agrícola de 2011/2012. Os tratamentos foram dispostos em delineamento de blocos ao acaso, em esquema fatorial 3 métodos de inoculação (tratamento de sementes, sulco de plantio e controle não inoculado) x 5 doses de nitrogênio (0, 75, 150, 225 e 300kg ha-1), com oito repetições. As variáveis analisadas foram: índice de área foliar (IAF), teor de N foliar, clorofila total, grãos por espiga e produtividade. Houve interação significativa entre os métodos de inoculação e a adubação nitrogenada para a variável IAF, mas não para a produtividade. Concluiu-se que a inoculação com a bactéria proporcionou incremento na produtividade de 702kg ha-1 para inoculação no sulco de semeadura e de 432kg ha-1 no tratamento de sementes, comparado com o controle, mas não houve diferença significativa entre esses dois tratamentos. Além disso, o teor de clorofila total, número de grãos por espiga e produtividade foram afetados positivamente, obtendo-se resposta quadrática, com aplicação da adubação nitrogenada

Nitrogen (N) is the most limiting nutrient for corn production. Thereby, the goal of the paper was to evaluate inoculation methods of Azospirillum brasilense in order to partially supply N required by the crop. The experiment was carried out in Guarapuava, PR, Brasil, in 2011/2012 growing season. Randomized blocks with factorial 3 inoculation methods (seed treatment, planting furrow and non-inoculated control) x 5 doses of nitrogen (0, 75, 150, 225 and 300kg ha-1) x 8 replications was used as the experimental design. Leaf are index, foliar nitrogen content, total chlorophyll, grains per ear and yield were evaluated. There was significant interaction between inoculation methods and nitrogen fertilization to leaf area index, but not for yield. Inoculation with the diazotrophic bacteria provided yield increase of 702kg ha-1 for inoculation in seeding furrow and 432kg ha-1 for inoculation in seed treatment compared to the control, but both treatments did not differ between each other. Furthermore, total chlorophyll, grains per ear and yield were positively affected, with quadratic response, by the nitrogen fertilization in broadcasting