Effect of integrated nutrient management on soil quality and productivity of soybean in Inceptisol

A field experiment was conducted to study the effect of integrated nutrient management (INM) on soil quality and productivity of soybean in an Inceptisol at Akola during 2010–11 to 2014–15 (5-years). The experiment consists of six treatments viz., absolute control, 100% recommended dose of fertilizers (RDF), 100% RDF + FYM @ 5 t ha-1, 50% RDF + 50% P through phosphocompost, 75% RDF + 25% N through cotton stalk, 100% RDF through FYM and remaining P applied through phosphocompost. The experiment was replicated four times in randomized block design. The results indicate that the average grain yield of soybean was increased with application of 100% RDF + FYM @ 5 t ha-1 (2.61 t ha-1). The physical (hydraulic conductivity and mean weight diameter), chemical (organic carbon, available N, P, K and DTPA extractable Zn, Fe, Mn and Cu) and biological properties viz., microbial biomass carbon and nitrogen, dehydrogenase activity (DHA), urease, alkaline phosphatase activity, nitrate reductase activity and microbial count were influenced significantly with the combined use of chemical fertilizer and organic manure. Application of 50% RDF + 50% P through phosphocompost proved beneficial in improving soil quality index (SQI). However, the sustainable yield index (SYI) was higher with the use of chemical fertilizer along with FYM @ 5 t ha-1 (0.92). The SQI was significantly and positively correlated with grain yield of soybean (R2 = 0.52*) and uptake of N (R2 = 0.78**), P (R2 = 0.70**) and K (R2 = 0.79**) by soybean. Among various key soil indicators, urease activity (29.9%) and CO2 evolution (67.1%) were found to be most important yield contributing parameters. The coefficient of determination was higher among soybean grain yield and total soil parameters (R2 = 0.77**) as against key soil indicators (R2 = 0.42*) indicating that all parameters contributed to the extent of 77% as against 42% contribution of key soil indicators.