Carbon mineralization dynamics of gangetic alluvial soil amended with fertilizers and plant growth-promoting microorganisms

Abstract

Carbon (C) storage and mineralization are highly linked with land use change. Quantification of C mineralization in soil under integrated nutrient management (INM) practices is essential to determine the extent of substituting inorganic fertilizers with organics. Therefore, a laboratory incubation study was conducted to evaluate the pattern of C mineralization in a horticultural soil amended with fertilizers and microbial agents over 90 days. Nine treatments including combinations of inorganic NPK fertilizers and plant growth-promoting microorganisms (PGPM), viz., Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis were applied in a completely randomized design with three replicates. The cumulative carbon dioxide (CO2) fluxes ranged from 46.20 mg CO2 100 g−1 soil (7-day) in unamended control to 137.25 mg CO2 100 g−1 soil (90-day) in 75% NPK + P. fluorescens + B. subtilis. Net C mineralization decreased significantly after 7 and 60 days of incubation and varied between 7.65 and 12.47 mg C 100 g−1 soil for control soil and between 8.94 and 22.59 mg C 100 g−1 soil for amended soils. However, C mineralization progressively decreased within 2 weeks of incubation period and continued the drop till 90 days. It ranged between 0.26 and 1.78 mg C 100 g−1 soil day−1 for unamended soil and between 0.30 and 3.23 mg C 100 g−1 soil day−1 for amended soils. The inclusion of bacterial agents in INM increased the decomposition rate in soil.