Improving Phosphate Efficiency by Phosphate Solubilizing Bacteria and Organic Matter Estimated by Radio Isotop (32P) Technique in Some Soils

Phosphorous (P) contents in many soils are varies highly along with their ability to provide available P to plant growth. Soils may contain very high in total P, but low in available P due to high P adsorbed by soil matrix and all their adsorbing agents. This research which using natural materials was aimed to increase P availability in some high-P absorption soils. The natural materials utilized for extracting P were organic matter, P extracting bacterial, androck phosphate. Those materials were interacted to high P absorption soils which were: Oxisol, Inceptisol, and Andisol. The detail objectives of this research were: (1) to study the potential of P-extracting agents (organic matter,and P-extracting bacteria) in releasing P of three high P- absorption soils; (2) to quantify the -age of P coming from the treatments; (3) to calculate the efficiency of P utilization by plant; and (4) to quantify Residual P in soils. The P mobility was analyzed by radioisotope technique using KH232PO4 carrier free solution. The results showed that adding soil organic matter increased the available P by 15.24% in Oxisol, 40.18 in Inceptisol, and by 7.34% in Andisol. Plant sorption toward P from % P used efficiency(%-PUE) up to 60 days was still very low, 0.65 to 9.34%.This was in accordance with the residual P in soils which were still quite high ranging from 94% to 96% in Andisol,91%97% in Inceptisol, and 96%-98% in Oxisol. The implication of the results of this research, however, is that the application of natural materials in improving soil P availability provides a longtimeresidual effect which could give benefit to the following crops.