Azospirillum spp. In grasses and forages. Review

Abstract

The Azospirillum genus includes plant growth-promoting bacteria found in different soil regions worldwide. When associated with plant roots these bacteria help augment productivity by increasing both the aerial and root portions. These benefits derive from excretion of growth phytonutrients, especially auxins. Use of Azospirillum spp. can help to bridge the gap between productivity and sustainability since inoculants based on this microorganism can reduce use of nitrogen fertilizers without affecting productivity, and generate savings and greater profitability. Inoculation of Azospirillum spp. strains with forage grasses can result in greater forage mass gains and less need for nitrogen fertilizer, improving pasture production system sustainability. Co-inoculation with other strains such as Bradyrhizobium sp. apparently potentiates growth promotion. Proper application methods must be followed for these growth-promoting bacteria to be effective. Growth promotion in response to Azospirillum has been described in grasses such as sugarcane, maize and forages, but further research is needed under different conditions to support adoption by producers. Application of bacterial inoculates can increase competitiveness vis-à-vis conventional agriculture methods. Inoculation of grasses in livestock systems can raise forage mass production, mitigate degradation risks and improve productive indices.