Combination of inoculation methods of Azospirilum brasilense with broadcasting of nitrogen fertilizer increases corn yield/Combinacao de metodos de inoculacao de Azospirillum brasiliense com adubacao nitrogenada de cobertura aumenta produtividade de milho

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.sup.-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.sup.-1] for inoculation in seeding furrow and 432kg [ha.sup.-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. Key words: nitrogen fertilization, diazotrophic bacteria, seed treatment, planting furrow. O nitrogenio (N) e o nutriente que mais limita a produtividade da cultura do milho. Dessa forma, o objetivo deste trabalho foi avaliar metodos de inoculacao de Azospirillum brasilense para suprir em parte o nitrogenio requerido pela cultura. O experimento foi conduzido em Guarapuava, PR, Brasil, no ano agricola de 2011/2012. Os tratamentos foram dispostos em delineamento de blocos ao acaso, em esquema fatorial 3 metodos de inoculacao (tratamento de sementes, sulco de plantio e controle nao inoculado) x 5 doses de nitrogenio (0, 75, 150, 225 e 300kg [ha.sup.-1]), com oito repeticoes. As variaveis analisadas foram: indice de area foliar (IAF), teor de N foliar, clorofila total, graos por espiga e produtividade. Houve interacao significativa entre os metodos de inoculacao e a adubacao nitrogenada para a variavel IAF, mas nao para a produtividade. Concluiu-se que a inoculacao com a bacteria proporcionou incremento na produtividade de 702kg [ha.sup.-1] para inoculacao no sulco de semeadura e de 432kg [ha.sup.-1] no tratamento de sementes, comparado com o controle, mas nao houve diferenca significativa entre esses dois tratamentos. Alem disso, o teor de clorofila total, numero de graos por espiga e produtividade foram afeta