The use of diazotrophic bacteria can help to achieve higher yields and reduce negative environmental impacts caused by N fertilizers. The aim of this study was to evaluate the effects of seed treatment with Azospirillum bacteria and the application of different rates of mineral N on maize agronomic performance at two levels of yield management. A field experiment was set up in Lages, SC, Brazil, in the 2011/2012 and 2012/2013 growing seasons. A randomized block experimental design arranged in split-split plots was used. Two yield management levels were tested in the main plots: medium (grain yield expectation of 8,000 kg ha-1) and high (grain yield expectation of 18,000 kg ha-1). Four N rates were assessed in the split plots, rates equivalent to 0, 0.5, 1.0, and 1.5 times the rate recommended by the Southern Brazil Commission of Soil Chemistry and Fertility to achieve the yield expectation at each level of yield management. The effect of seed treatment with Azospirillum sp. was evaluated in the split-split plots. Grain yield ranged from 8,344 to 16,947 kg ha-1 at the high management level and increased quadratically with the increase in N rate, both with and without Azospirillum seed treatment. At the medium management level, grain yield ranged from 5,986 to 9,684 kg ha-1. It increased linearly with the increase in N rate when seeds were treated with Azospirillum and was not affected by mineral N in treatments without seed inoculation. The efficiency of N use decreased when Nn rates increased at both yield management levels and whether the seeds were inoculated or not. There was no significant difference in grain yield between inoculated and non-inoculated treatments, regardless of the yield management level or N rate. Therefore, seed treatment with Azospirillum sp. did not improve the agronomic performance of maize.
Zea mays; inoculation; diazotrophic bacteria; sidedress nitrogen
