Abundance, diversity and prospecting of culturable phosphate solubilizing bacteria on soils under crop-pasture rotations in a no-tillage regime in Uruguay

Phosphate solubilizing bacteria (PSB) abundance and diversity were examined during two consecutive years, 2007 and 2008, in a crop/pasture rotation experiment in Uruguay. The study site comprised five treatments with different soil use intensity under a no-tillage regime. In the first year of sampling, abundance of PSB was significantly higher in natural prairie (NP) and permanent pasture (PP) than in continuous cropping (CC); rotation treatments harbored populations that did not differ significantly from those in the others. The percentage of PSB relative to total heterotrophic bacteria ranged between 0.18% and 13.13%. PSB diversity also showed statistical differences among treatments, with PP populations more diverse than those present in CC. In the second year sampled no differences were found in PSB abundance or diversity. Two hundred and fifty PSB were isolated in 2007 and classified according to their phosphate solubilization activity in vitro. Twelve of these isolates showing the greatest solubilization activity were selected for 16S rDNA sequencing. Ten isolates presumably belong to the genus Pseudomonas and two isolates showed high similarity with members of the genera Burkholderia and Acinetobacter. © 2011 Elsevier B.V.