Plant-Growth Promotion in Natural Pastures by Inoculation with Azospirillum brasilense Under Suboptimal Growth Conditions

Inoculation experiments of natural pastures with the rhizobacterium Azospirillum brasilense were conducted in Israel in 1996, in two climatically differentiated regions. These experiments were carried out as part of a project with the objective of estimating the potential of the inoculation technique in improving pasture yields. The effects of inoculation with A. brasilense were compared to P-fertilization and to untreated controls. In two semiarid sites, it was generally observed that both the inoculation and the P-fertilization treatments increased pasture yield as measured by dry weight biomass. It was also found that both inoculation and P-fertilization treatments caused an enrichment in legumes relatively to grasses and forbs. Despite the ecological complexity of these sites and the variability of the data, statistical significance was generally achieved. In a more topographically uniform site, located in a typical Mediterranean climate, the positive effects of A. brasilense inoculation in plant-growth were substantially clear, with final yields duplicated in both inoculation and combined (inoculation and P-fertilization) treatments in comparison to P-fertilization alone and untreated controls. The potential of using A. brasilense for growth promotion of natural pastures is discussed.