IMPROVING THE SOLUBILITY OF EPPAWALA ROCK PHOSPHATE BY DIFFERENT AMENDMENTS AS ALTERNATIVES FOR IMPROVING PHOSPHORUS UPTAKE IN MAIZE CULTIVATION

Abstract

Eppawala Rock Phosphate (ERP) may be an alternative to imported Triple Super Phosphate (TSP) for certain annual crops like maize, despite its reduced solubility, which limits direct application for annual crops. The potential of using biochar and vermicompost blended with ERP as a substitute for TSP in maize cultivation was evaluated by conducting a field trial at the Grain Legumes and Oil Crops Research and Development Center, Angunakolapelessa. The field experiments were conducted with eight treatments: T1: Control, T2: Department of Agriculture (DOA) Recommended (Rec.) mineral only, T3: DOA Recommendation (mineral + Organic 10 t ha-1), T4: DOA Rec. N, K + 75% TSP + 25% ERP, T5: DOA Rec. N, K + 50% TSP + 50% ERP + vermicompost (2 t ha-1 ), T6: DOA Rec N, K + ERP matured with vermicompost (1:4 ratio), T7: DOA Rec. N, K + 50% TSP + 50% ERP matured with vermicompost, T8: DOA Rec. N, K + 50% TSP + 50% ERP with biochar-based pellet. Treatments of the field trial were arranged in a randomized complete block design with three replicates. The soil and plant growth parameters of different treatments were compared statistically, and the mean comparison was done using the LSD test. Results indicated significantly (p≤0.05) higher plant height (203 cm) and shoot dry matter weight (403 g) in T4 compared to the rest. The available soil phosphorus contents of T4 (13.6 mg g-1and T7 (14.5 mg g-1) were significantly higher (p≤0.05)compared to the T2 (10.73 mg g-1). In contrast, plant height, shoot dry weight, and available soil P content of T6, where ERP was the sole P source, were similar with the same parameters of T2. Therefore, T6 is a better alternative to reduce the application of TSP for early growth in maize cultivation.