Effect of phosphate solubilizing bacterium, vermicompost and phosphate sources on growth of lettuce in a calcareous soil

Co-application of biological fertilizers and phosphate sources have greatly considered in calcareous soilsin recent years. In order to study the effect of phosphate solubilizing bacterium (PSB), phosphate sources and vermicompost on some growth characteristics of lettuce (cv. Ferdos), a greenhouse experiment was conducted with factorial arrangement in a completely randomized design with three replications and three factors. Factors consisted of two levels of phosphate solubilizing bacterium (Pseudomonas flouresence) (with and without inoculation), two levels of vermicompost (0 and 1% w/w) and four phosphate sources (control, rock phosphate, tricalcium phosphate (TCP) and triple super phosphate at 25 mg P kg-1 soil). Biological fertilizers significantly increased shoot fresh and dry weights (SFDW), but they didn’t have remarkable effect on lettuce height. Application of rock phosphate and tricalcium phosphate (TCP) increased dry and fresh weight, respectively. Application of triple super phosphate significantly increased SFDW and lettuce height. Co-application treatments of bacterium, vermicompost and phosphate sources (except super phosphate) significantly increased SFDW, leave numbers and phosphorus concentration of lettuce. Overall, the results indicated that phosphorus chemical fertilizers can be replaced by co-application of insoluble phosphate and biological fertilizers.