Biofertilization with Rhizoglomus irregularulare and Azospirillum brasilense in Brachiaria hybrid cv. Mulato II

Abstract

An experiment was carried out with the objective of evaluating the effect of biofertilization with the plant growth promoting bacteria Azospirillum brasilense and the arbuscular mycorrhizal fungus Rhizoglomus irregulare in Brachiaria hybrid grass cv. Mulato II cultivated in a Mollic Carbonated Cambisol. It included four treatments formed by the inoculation, alone and in combination, of both microorganisms plus a control without inoculation, in a Latin Square design. The inoculum with R. irregulare had a concentration of 30 g^-1spores and was applied by the method of coating the seeds, while A. Brasilense, with a concentration of 10⁹ CFU mL^-1, was applied by embedding the seeds at the time of planting, and at a rate of 20 L ha^-1after the first cut. Four cuts were made, at intervals of 60 and 90 days in the rainy and dry season, respectively. R. irregulare increased the frequency and intensity of mycorrhizal colonization, as well as the number of spores in the rhizosphere, although the greatest results were achieved when applied with A. brasilense. Biofertilizers separately increased the growth of the aerial and radical part of the plants, the nitrogen concentrations in the aerial biomass and the dry mass yield of the grass, but the higher values of these variables, as well as the greater contribution of the biofertilization in Nitrogen grass nutrition was obtained with its joint application. The effect of biofertilization was maintained for one year.