Liquid Bioformulation Regulates Soil Microbial and Enzymatic Activities, and Nutrient Dynamics in Drip-Irrigated Aerobic Rice

Abstract

ABSTRACT The use of liquid formulations―prepared from naturally available farm wastes―has increasingly gained popularity in recent years; however, it remains unclear how these amendments influence the rhizosphere soil biochemistry, particularly in aerobic rice. In this study, we reformulated the traditional liquid manure (Jeevamrutha) with microbial consortia as liquid bioformulation (LBF), and evaluated its potential effect (when applied with or without NPK-fertilizers) on soil biochemical properties and nutrient availability at different stages of crop growth. Six treatments were tested: (i) absolute control, (ii) conventional practice (CP), LBF applied twice at 2000 L ha–1 with (iii) 100% recommended dose of fertilizer (RDF) through a multi-split fertigation (LBF+NPK100), (iv) 75% RDF (LBF+NPK75), (v) 50% RDF (LBF+NPK50), and (vi) LBF alone. The results showed that soil microbial biomass carbon, total bacterial and fungal load, dehydrogenase, urease, and acid phosphatase activities were significantly (p < .05) higher in the LBF co-applied plots, particularly at the panicle initiation and maturity stages of rice. However, actinomycetes and alkaline phosphatase showed an irregular trend with the growth stages. The rhizosphere soil microbial index (RSMI) values were significantly higher under LBF co-applied treatments over the CP, signifying the improvement of soil quality. Grain yield with LBF+NPK75 increased by 30.3−37.8% and 19.3−32.4% for the summer and rainy seasons, respectively, compared with the CP. Combining LBF with NPK-fertigation had more long-lasting effect on soil N and P availability. Therefore, our findings suggest that substituting about half of RDF with LBF could bring promising agronomic and soil ecological benefits to the rice production under aerobic conditions.