Nitrogen fertilization associated with Azospirillum brasilense inoculation in the maize crop

The use of plant growth-promoting bacteria has proven to be a promising alternative for maize crops. The aim of this study was to evaluate the vegetative growth of maize under different mineral nitrogen doses and inoculation with Azospirillum brasilense. The experiment was conducted under protected cultivation, using a randomized block design with 20 treatments and 4 replications, arranged in a 2 x 2 x 5 factorial scheme. The treatments included inoculation with A. brasilense and control (no inoculation), two water conditions (irrigated and water suppression), and five N doses: 0, 40, 80, 120 and 160 kg ha-1, resulting in a total of 80 experimental units. The results showed no significant interaction between A. brasilense inoculation and nitrogen doses. The 160 kg ha-1 N application resulted in increases in plant height at 20 DAE (days after emergence), stem diameter, live leaves total number and total chlorophyll index. The 120 kg ha-1 N application led to increases in plant height, root dry mass, root volume and root fresh mass at 90 DAE. The live leaves number, total leaves, plant height, total chlorophyll and leaf temperature were higher in the treatments without water suppression. Water suppression, however, promoted greater root volume development when combined with the microorganism’s application. It can therefore be concluded that, under the conditions tested in this study, the maize vegetative growth can be influenced by different N doses, regardless of inoculation with A. brasilense.