Phosphate Solubilizing Bacteria (PSB) Improve Phosphorus Availability from Various Sources in Alkaline Soils

Phosphorus (P) is one of the major essential macronutrients for plants, applied to soil in the form of phosphatic fertilizers and organic manures. The application of PSB to soils can replace or partially reduce use of inorganic P fertilizers and could be one of the cost effective, highly efficient, and sustainable approaches to conserve P resources. The aim of the study was to evaluate the role of PSB in phosphorus (P) availability from organic, mineral and natural sources. For this purpose, a laboratory incubation experiment was conducted at the University of Agriculture Peshawar.  The experiment was consisting of four sources of P [poultry manure (PM), farm yard manure (FYM), rock phosphate (RP) and single supper phosphate (SSP)] for obtaining 45 mg P2O5 kg-1 and two types of inoculation (control and PSB) arranged in two factorial complete randomized design with three replications. Resultantly, PSB inoculation significantly improved. P availability at all incubation interval except day zero. A 3.4%, 5.4%, 12% and 16 % increased were observed in P as compared to control, at day 7, 14, 28 and 56 respectively.  Similarly, significant differences were observed in P release for P sources at all incubation intervals. Initially higher P release was observed for SSP but at day 14 onward PM and FYM proved to be the best P releasable sources as compared to mineral P sources. RP released the lowest P at all incubation intervals however it performed statistically at par to SSP at 56 days.  The significant interactive effect of P sources and PSB at day 28 and 56 demonstrated that soil receiving P from organic sources inoculated with PSB released higher P than other treatments combination. Thus, it is suggested that P must be applied from organic P sources (PM and FYM) along with PSB inoculation for better P nutrition and crop yield.