Utilização de Azospirillum spp. na sustentabilidade de sistemas pastoris de capim-marandu no bioma cerrado

Abstract

In Brazil, livestock farming depends mainly on pastures as a source of feed for cattle. Within this scenario, it is essential to highlight the environmental role of the vast areas of pasture, especially due to their ability to sequester atmospheric carbon. It is estimated that the country has approximately 177 million hectares of pastures, most of which are covered by plants of the genus Brachiaria syn. Urochloa. Among the Brachiaria species, B. brizantha (Hochst. ex A. Rich.) Stapf. cultivar Marandu is the most cultivated, occupying more than 50 million hectares. In the Cerrado region, the introduction of Brachiaria has made it possible to increase the support capacity of pastures by up to three times and in 2023 the Biome had more than 56 million hectares of pasture mapped, with approximately 67% of this area in some stage of degradation, compromising the potential for carbon sequestration, as well as soil health and conservation, animal productivity, economic sustainability, among others. The use of inoculants that favor the use of atmospheric nitrogen and/or promote an increase in plant biomass, through greater root development, can improve this scenario, contributing to the recovery of soil fertility and increased productivity. Thus, in order to understand the role of Azospirillum spp. and investigate their advantages in increasing production, a literature review and meta-analysis study was carried out with the aim of establishing the most efficient technological format for the use of these microorganisms in Marandu grass pastures, in the different conditions studied by researchers, notably in the Cerrado biome. In this context, it can be concluded that Azospirillum synergistically enhances the use of nitrogen, promoting an increase of up to 45% in tillering. It can also increase biomass production by up to 75% and root production by up to 79%, depending on the dose of nitrogen applied. By fixing atmospheric N or increasing the efficiency of fertilizers, the use of these bacteria can improve plant nutrition and soil fertility, providing greater carbon sequestration which in turn will be transformed into milk and/or meat in less time, directly reducing greenhouse gas emissions. This results in greater profitability and sustainability.