USE OF SOIL MICROBIAL CULTURES TO INCREASE THE SOLUBILITY OF PHOSPHORUS IN EPPAWALA ROCK PHOSPHATE

Abstract

At present, Sri Lanka imports phosphorus fertilizers incurring a lot of foreign exchange even though there is a high-quality apatite deposit at Eppawala. Eppawala rock phosphate (ERP) can be utilized as a Phosphorus fertilizer having increased the water solubility of rock phosphate through chemical or biological processes. However, biological processes are more cost-effective and ecofriendly. Thus, the study focused to increase the solubility of ERP using the selected soil microbes. Soil samples which contain different microbes were collected using a simple random sampling method (n-30) from five forested areas (Badagamuwa, Sinharaja, Diyathalawa Turpentine, Girandurukotte Teak, and Nonperial Pinus plantations) considering the phosphorus level in the soil, distribution in Sri Lanka, and microbial count in the soil. Microbial rich cultures were prepared by using the obtained soil samples and applied to the ERP. A randomized complete block design (RCBD) was used for the experiment with 5 replicates for each treatment and only ERP was used as a control. Treated samples were tested for the available phosphorus percentage using the Ascorbic acid method during 8 weeks within a week interval. The results were statistically analyzed using two-way ANOVA and Tukey pairwise comparison test (95% confidence interval). The available phosphorus percentages of all treated samples were significantly higher (p<0.05) than the controlled samples in every week. The highest available phosphorus percentages of all treated ERP samples were in 0.75% - 0.81% range while controlled (ERP) was 0.42%, which significantly recorded (p<0.05) in 6th week. Selected soil microbial cultures increased the solubility of ERP and therefore ERP can be utilized as a phosphorus fertilizer with applying the further improved microbial cultures