A framework for refining soil microbial indices as bioindicators during decomposition of various organic residues in a sandy loam soil

Abstract

Assessment of soil quality is an invaluable tool in determining the sustainability and environmental impact of agricultural ecosystems. Soil microbial indices like microbial biomass and microbial activity are important criteria for the determination of soil quality. Laboratory incubation study was undertaken to examine the influence of eight crop residues widely varying in biochemical composition on the periodic changes in important soil microbial indices {(microbial (Cmic: Corg), metabolic (qCO2), carbon mineralization (qC) and microbial biomass change rate (qM) quotients)} at 28 days and 63 days after incubation (DAI) in a sandy loam soil. A. sativa amended soil showed maximum soil respiration rate (14.23 mg CO2-C g-1 soil day-1) whereas T. aestivum amended soil showed maximum microbial biomass C (790 µg/g). The metabolic quotient among different crop residues ranged from 11.1 to 19.8 ?g CO2-C ?g-biomass-C-1 h-1 at 63 DAI. The results indicate that incorporation of different crop residues has positive effect on microbial flora and their activity. Microbial quotient (Cmic:Corg) was significantly positively correlated with microbial biomass carbon (MBC), qC and qM. The study suggests that the biochemical composition of different crop residues seems to be of better option for long term sustainable crop production with maintenance of soil quality in a sandy loam soil.