Biofilm Enriched rock phosphate as a potential phosphorous fertilizer to replace triple super phosphate in rice cultivation: A preliminary field trial

Abstract

Rock Phosphate (RP), derived from natural apatite mined from Eppawala (ERP), is identified as a possible substitute for Triple Super Phosphate (TSP). However, its application is limited due to low solubility. If the bio-solubility is enhanced, ERP can be used as a phosphorous (P) fertilizer for annual crops. The present study focused on using an effective biofilm formulation identified after screening several known phosphate solubilizing biofilms, and introducing a biofilm-enriched ERP (BEE) as an alternative for TSP in rice cultivation. Two field trials were conducted in two consecutive seasons, dry season in 2018 (Yala) and the wet in 2018/2019 (Maha). The existing chemical fertilizer dosage (CF) recommended for rice by the Department of Agriculture (DOA) was modified by fully replacing TSP-P with BEE, along with 65% nitrogen (N) and potassium (K) fertilizers (CFNK). Three different rates of BEE, 65, 80 and 100% (equivalent to TSP-P recommended by the DOA) were tested (CFNK + 65 BEE, CFNK + 80 BEE and CFNK + 100 BEE) against CF. Results revealed that the rate of 100% BEE performed better than that of other rates of BEE (65% and 80%), while the same recorded significantly higher grain yields in both seasons compared to all other treatments. Moreover, plant growth parameters viz. shoot and root dry masses, height, and panicle length were also recorded higher values with CFNK + 100BEE application than the control (CF). Therefore, the BEE can be suggested as an alternative to TSP for rice cultivation, with an added advantage of using a reduced dosage of N and K fertilizers. However, further studies are needed to test the BEE under different soil and climatic conditions in the country.