Effects of phosphate solubilizing bacteria and phosphorous levels on Rice (Oryza sativa L.)

In order to study the effects of phosphate solubilizing bacteria and of rates of phosphorous application on the growth and yield of rice cultivar Shiroodi, an experiment was conducted in the split plot format using the randomized complete block design in four replications in the city of Neka of northern Iran in 2012. The experimental treatments included three rates of phosphorous application (zero, 83, and 165 Kg.h) in the form of concentrated superphosphate as the major factor, and four types of biofertilizers (not inoculated with bacteria, inoculated with Pseudomonas fluorescens, inoculated with Pseudomonas putida, and simultaneously inoculated with both Pseudomonas fluorescens and Pseudomonas putida) as the minor factor. Results obtained indicated that application of mineral phosphorous caused an increase in seed yield of the rice cultivar Shiroodi so that the maximum seed yield (630.251 g.m2) was obtained in the treatment of applying 165 Kg.h phosphorous. The increase of seed yield in this treatment was accompanied with the maximum number of tillers (23.981), the longest panicles (27.209 cm), and the largest number of seeds per panicle (116.30). It was also observed that inoculation with bacteria improved the yield and yield components of the rice cultivar Shiroodi so that the maximum number tillers (22.46), the highest percentage of fertile tillers (94.64), the longest panicles (26.29 cm), and the largest number of seeds per panicle (104.95) were observed when seeds were simultaneously inoculated with both bacterial species. With respect to seed yield, it was found that the use of a single bacterial species, as compared with the employment of two bacterial strains, caused a greater increase in seed yield so that the maximum seed yields of 594.97 and 594.85 g.m2 were obtained when the putida or the fluorescens species were used, respectively. With regard to the Interaction effects of the application of mineral phosphorous and inoculation with bacteria also, the highest seed yield (696.91 g.m2) was observed under the interaction effects of applying 83 Kg of mineral phosphorous and inoculating with Pseudomonas putida. This was accompanied by the maximum percentage of fertile tillers (94.24%), long panicles (26.09 cm), and a considerable 1000 –seed weight (22.80 g).