[In Press] Bacillus megaterium-embedded organo biochar phosphorous fertilizer improves soil microbiome and nutrient availability to enhance black gram (Vigna mungo L) growth and yield

Phosphorus (P) deficiency in low-pH soils adversely affects blackgram (Vigna mungo L) productivity. In low-pH soils, phosphorus binds with iron and aluminium to form insoluble phosphate complexes, resulting in reduced phosphorus availability to plants. Chelating phosphorus with organic materials would improve crop growth and yield by increasing the availability and utilization of applied phosphorus. In this respect, biochar, farmyard manures (FYM) and phosphate-solubilizing bacteria have been used to chelate inorganic phosphorus and modify the P availability. However, little is known about the interaction between biochar, farmyard manure, phosphate-solubilizing bacteria and phosphorus fertilizers in low-pH soils. To study the interactions, we prepared ten P fertilizer formulations involving two P fertilizer sources (superphosphate and rock phosphate), two organic amendments (biochar and farmyard manure) and a phosphate-solubilizing bacteria (Bacillus megaterium). Two field experiments were conducted in low-pH soils (6.29) over two years to evaluate the performance of these P formulations in terms of phosphorus availability, uptake, bacterial diversity and blackgram yield. Application of Bacillus fortified superphosphate organo-biochar formulation at 750 kg ha(- 1) showed higher soil available P (9.7 mg kg(- 1)) and uptake (15.1 kg ha(- 1)), resulting in a 13 and 24% increase in P availability and uptake compared to superphosphate alone. In the same formulation, soil microbial biomass phosphorus, microbial biomass carbon, acid phosphatase and bacterial diversity were also higher, resulting in better growth and seed yield (1034 kg ha(- 1)) in comparison to superphosphate alone. Applying bacillus-embedded farmyard manure and biochar enriched superphosphate at 750 kg ha(- 1) containing 50 kg of phosphorus and 2 kg of bacillus can be adopted to increase phosphorus availability, utilization, microbial diversity and blackgram production in low pH soils.