Can Biofilm-Enriched Eppawala Rock Phosphate Replace the Use of Triple Super Phosphate in Rice Cultivation?

Abstract

Eppawala Rock Phosphates (ERP) has a greater potential to be used as an alternate for Triple Super Phosphate (TSP) if phosphorous (P) biosolubility is increased. A certain biofilm (BF3) has been identified as the most efficient P biosolubiliser for ERP. Thus, this study was designed to test the potential of replacing TSP from biofilm-enriched ERP in rice cultivation. Two experiments were conducted; soil leaching tube and pot experiments under controlled conditions. A modified chemical fertiliser (CFM) mixture was developed by replacing TSP from ERP, in the existing chemical fertiliser (CFE) mixture for rice recommended by the Department of Agriculture (DOA). Eleven treatments were used with all possible combinations of CFE and CFM at rates of 50% or 100% alone or together with the BF3. Soil alone was used as the control. Treatment of 50% CFM+BF3 was denoted as biofilm-enriched ERP. The experiments were conducted in a completely randomized design (CRD) with three replicates. Data were statistically analyzed using analysis of variance (ANOVA) followed by mean separation using Turkey’s HSD test. Solubilised P was recovered by leaching in every two weeks for three months. Available soil P, total plant P and grain yields were evaluated at the end of the pot experiment. Biofilm enriched ERP showed no added advantage over the CFE, with lower cumulative solubilized P in leachates. At the end of the pot experiment; biofilm-enriched ERP showed significantly (p<0.05) higher P retention in soil and significantly (p<0.05) lower grain yield comparison to the CFE. However, biofilm-enriched ERP showed no any significant (p>0.05) difference in total plant P. The overall results conclude that the biofilm-enriched ERP performed poorly in comparison to the DOA recommended TSP dosages. Thus, further studies are required to enhance the performance of biofilm-enriched ERP to use as an alternate for TSP in rice cultivation.
Keywords: Biofilm, Eppawala Rock phosphate, Rice cultivation, Triple super phosphate