Inoculation of diazotrophic bacteria modifies the growth rate and grain yield of maize at different levels of nitrogen supply

This work intended to evaluate the contribution of single inoculation of diazotrophic bacteria Herbaspirillum seropedicae or Azospirillum brasilense on growth and yield of maize crop at different levels of N fertilization. Two field experiments were carried out in the summer and winter seasons. Factorial design combined four fertilization levels (0, 50, 100 and 150 kg N ha(-1)) and three seed inoculations (non-inoculation, strains Hs-ZAE94 or Ab-Sp245), with four replications. Shoot dry matter, leaf area index, and N accumulation were evaluated in weekly samplings, and grain yield measured at maturity. Most expressive responses of inoculation were observed in the summer crop, with minor effects in the winter crop when growth and yield were lower. In the summer, inoculation increased shoot dry matter and leaf area of maize plants, enhancing crop growth rate, and increased N accumulated by shoots, particularly at low levels of N supply. In the summer, Hs-ZAE94 increased grain yield at the levels of 0, 50 and 100 kg N ha(-1), and Ab-Sp245 at 100 kg N ha(-1), as compared to non-inoculation. Inoculation with Hs-ZAE94 associated with 50 kg N ha(-1) provided similar grain yield than the non-inoculation with 150 kg N ha(-1), improving N use efficiency.