Synergistic effects of steel slag and microbial inoculants on physiochemical and biological soil properties under variable NPK fertilization

This study investigated the synergistic effects of steel slag (0.5 and 1.0 ton ha⁻¹) and microbial inoculants (PSB and PSF) on soil physiochemical and biological properties under variable NPK fertilization regimes across two growing seasons (2020-21 and 2021-22). A randomized pot experiment with seventeen treatments evaluated soil pH, electrical conductivity, nutrient availability (N, P, K), total microbial count, dehydrogenase activity, and urease activity. Results demonstrated that combined applications of steel slag with microbial inoculants significantly enhanced soil biological activity and nutrient availability compared to conventional NPK treatments. The integration of dual microbial inoculants (PSB and PSF) with reduced NPK levels showed superior performance in phosphorus availability and dehydrogenase activity, while steel slag amendments combined with microbial inoculants optimized potassium availability and enhanced microbial populations. Steel slag application rates of 0.5-1.0 ton per hectare effectively improved soil enzymatic activities and maintained favorable soil pH and electrical conductivity levels. The synergistic combination of steel slag and microbial inoculants with reduced NPK fertilization proved highly effective in improving soil health parameters while maintaining nutrient balance.