Phosphate Solubilization and Plant Growth-Promoting Potential of Penicillium oxalicum (Bt9) in Eppawala Rock Phosphate-Enriched Compost

Abstract

The frequent application of chemical phosphate (P) fertilizers is costly and has emerged as a key issue in the current agriculture sector of Sri Lanka. Hence, the present study evaluated the impact of fungal inoculum Penicillium oxalicum (Bt9), on bio-solubilization of Eppawala Rock Phosphate (ERP) enriched compost. A Completely Randomized Design (CRD) was applied as the experimental design, involving four compost treatments. Each treatment was replicated four times. Treatment1 (T1) was incorporated with P. oxalicum (Bt9) + sugar, Treatment 2 (T2) was incorporated solely with P. oxalicum (Bt9), Treatment (T3) was incorporated solely with sugar and Treatment (T4) as the control, lack of both P. oxalicum (Bt9) and sugar. The Molybdenum blue method evaluated each treatment's released bioavailable Phosphorus (P) content. A pot experiment was conducted for red cowpea (Vigna unguiculata) using phospho-compost and soil in a 1:1 ratio to evaluate the impact of bio solubilization of ERP in compost by P. oxalicum (Bt9) on plant growth. The results exhibited significantly higher (p ≤ 0.05) plant growth parameter values (shoot length, root length, and total plant length) in Treatment 1 and 2 compared to Treatment 3 and 4. The highest shoot length, root length, and total plant length were recorded in Treatment 1, and the respective measurements were; 26.58 ± 2.44 cm, 11.36 ± 1.48 cm and 54.24 ± 2.64 cm. This study concluded that P. oxalicum (Bt9) significantly increased the solubilization of phosphate and promoted the plant growth of red cowpea (Vigna unguiculata). Thus, ERP - enriched compost inoculated with P. oxalicum (Bt9) can be considered as a sustainable alternative to the imported chemical P- fertilizer.