A phosphate-solubilizing bacteria based biofertilizer applied with Eppawala rock phosphate as a strategy to supply phosphorous in rice (Oryza sativa) cultivation

Abstract

Concerns regarding environment and economics necessitate sustainable alternatives for synthetic phosphorous (P) fertilizers like triple-superphosphate (TSP). This study aimed to assess the efficacy of a Phosphate-Solubilizing Bacteria (PSB) based biofertilizer in solubilizing Eppawala Rock Phosphate (ERP) to supply P required for paddy cultivation. Experiments were performed in a plant house and farmer’s fields. Four treatments, equivalent to field recommendations (T1- zero P, T2- P applied as TSP at 60 kg/ha, T3- P applied as ERP at 90 kg/ha, T4- T3 with PSB) were used to grow Bg360 variety in pot-experiment with six replicates, and growth and yield parameters were determined. Treatments T2, T3 and T4 were repeated in a field study in “Yala” 2022 in four farm fields in Matale district, Sri Lanka (plot size = 100 m2 per treatment). Each farm field served as a replicate. Soils collected before crop establishment and after harvest were characterized. Rice yield, yield parameters and P uptake in grains were determined at the time of harvest. Dry weights of shoots and roots, and plant nutrition levels were determined at the end of the vegetative and harvesting stages. Analysis of variance (ANOVA) was performed on data and means were compared using Tukey’s HSD test. In the pot-experiment, T2 resulted in the highest grain yield (1.36±0.05 g/plant) and P content in grains (0.26±0.01%). However, plant growth and grain yield were comparable (P>0.05) among T2 and T4, and significantly higher (P<0.05) than those under T1 and T3. Melich-3 extractable soil P content increased significantly in T2 (9.11±0.36 mg/kg) followed by T4 (7.41±0.13 mg/kg) compared to initial P level (6.12±2.26 mg/kg). In the field experiment, the treatment effect was not significant (P>0.05) on grain yield or yield parameters. The average grain yield under T2, T3 and T4 were 5572.00±1512.71, 3968.29±1258.56 and 4113.88±1174.66 kg/ha, respectively (expected yield; 4300 kg/ha). Results indicate application of PSB-biofertilizer increased P availability from ERP to the crop. PSB together with ERP can be used to supply P without compromising paddy yield in the studied region. The biofertilizer should investigate further under field conditions to establish as a sustainable approach for P management in paddy cultivation.