Field scale responses of soil enzymatic activities and microbial indicators to combined bioinoculant-fertilizer management in mustard (Brassica juncea L.)

Nutrient management plays a crucial role in optimizing crop yield while ensuring soil sustainability. However, there is a need to explore balanced approaches that reduce chemical fertilizer dependency without compromising productivity. This study investigates the effects of nutrient regime and microbial inoculant on the soil enzymatic activities, microbial populations, soil nutrient dynamics and yield of Indian mustard (Brassica juncea L.). The experiment, conducted over two cropping seasons (2021–22 and 2022–23) at the Agricultural Research Farm, Banaras Hindu University, employed a split-plot design with three main plots (Nutrient regime) and six sub-plots (Microbial inoculant). Results demonstrated that the application of 100% Recommended Dose of Fertilizer (RDF) significantly enhanced growth parameters, yield attributes, and overall productivity of mustard. The integration of microbial inoculants, particularly NPK consortia combined with Zinc Solubilizing Bacteria (ZSB), showed remarkable improvements in soil microbial populations, enzyme activities, and nutrient availability. Although 75% RDF resulted in slightly lower yield and growth compared to 100% RDF, it was not far behind, and when combined with NPK consortia and ZSB, it emerged as a promising sustainable alternative. Principal Component Analysis (PCA) further confirmed the strong positive correlations between yield attributes, soil nutrient availability, and enzyme activities.