Development and yield of maize in response to inoculation of associative diazotrophic bacteria and nitrogen doses

Abstract

The use of diazotrophic bacteria features an important alternative to nitrogen (N) supply to crops. However, the efficiency of biological nitrogen fixation (BNF) depends on the capacity of bacterial-plant interaction. One strategy to improve this interaction is to select bacterial strains adapted to local edaphoclimatic conditions. Thus, we hypothesized that diazotrophic bacteria isolated under local edaphoclimatic conditions have a better efficiency of interaction with the plant, resulting in a greater N supply capacity for the Zea mays crop. This study evaluated the effects of inoculation of diazotrophic bacteria and N doses on the development, yield and nutrition of maize grown in Campo Verde (Mato Grosso, Brazil) in the 2013/2014 crop season. The experiment was conducted under a randomized block design in bifactorial scheme 4×3. The treatments consisted of a commercial inoculant (strains Ab-V5 and Ab-V6 of Azospirillum brasilense), two isolates of associative diazotrophic bacteria (MTAz8 and MTh2, similar to Azospirillum sp. and Bacillus sp., respectively) and absence of inoculation (control), combined with three N doses (0, 55 and 110 kg·ha -1 ) with four replicates. Plant height, spike insertion, stem diameter, chlorophyll index, N concentration in leaves and grains, grain yield and aboveground dry matter were evaluated. There was significant interaction of inoculation and N doses in aboveground dry matter. The other variables, except for stem diameter, were influenced by only one factor, inoculation or N doses. Our results show that inoculation of isolates MTAz8 and MTh2 promotes a substantial increase in the production of aboveground dry matter in relation to the commercial inoculant, confirming our hypothesis. In addition, our results suggest that inoculation promotes increases in grain yield, even without application of N fertilizer.