The impact of global warming on soil carbon (C) mineralization from bulk and aggregated soil in conservation agriculture (CA) is noteworthy to predict the future of C cycle. Therefore, sensitivity of soil C mineralization to temperature was studied from 18 years of a CA experiment under rice-wheat cropping system in the Indo-Gangetic Plains (IGP). The experiment comprised of three tillage systems: zero tillage (ZT), conventional tillage (CT), and strip tillage (ST), each with three levels of residue management: residue removal (NR), residue burning (RB), and residue retention (R). Cumulative carbon mineralization (Ct) in the 0-5 cm soil depth was significantly higher in CT with added residues (CT-R) and ZT with added residues (ZT-R) compared with the CT without residues (CT-NR). It resulted in higher CO2 evolution in CT-R and ZT-R. The plots, having crop residue in both CT and ZT system, had higher (p < 0.05) Van't-Hoff factor (Q10) and activation energy (Ea) than the residue burning. Notably, micro-aggregates had significantly higher Ea than bulk soil (~14%) and macro-aggregates (~40%). Aggregate-associated C content was higher in ZT compared with CT (p < 0.05). Conventional tillage with residue burning had a reduced glomalin content and β-D-glucosidase activity than that of ZT-R. The ZT-R improved the aggregate-associated C that could sustain the soil biological diversity in the long-run possibly due to higher physical, chemical, and matrix-mediated protection of SOC. Thus, it is advisable to maintain the crop residues on the soil surface in ZT condition (~CA) to cut back on valuable C from soils under IGP and similar agro-ecologies.
Keywords: activation energy; aggregate-associated carbon; carbon mineralization; glomalin; temperature sensitivity of SOC decomposition (Q10).