Plant-growth promotion in natural pastures by inoculation with Azospirillum brasilense under suboptimal growth conditions

Inoculation experiments of natural pastures with the rhizobacterium Azospir illum brasilense were conducted in Israel in 1996, in two climatically diff erentiated regions. These experiments were carried out as part of a project with the objective of estimating the potential of the inoculation techniqu e in improving pasture yields. The effects of inoculation with A. brasilens e were compared to P-fertilization and to untreated controls. In two semiar id sites, it was generally observed that both the inoculation and the P-fer tilization treatments increased pasture yield as measured by dry weight bio mass. It was also found that bath inoculation and P-fertilization treatment s caused an enrichment in legumes relatively to grasses and forbs. Despite the ecological complexity of these sites and the variability of the data, s tatistical significance was generally achieved. In a more topographically u niform site, located in a typical Mediterranean climate, the positive effec ts of A. brasilense inoculation in plant-growth were substantially clear, w ith final yields duplicated in both inoculation and combined (inoculation a nd P-fertilization) treatments in comparison to P-fertilization alone and u ntreated controls. The potential of using A. brasilense for growth promotio n of natural pastures is discussed.