Aggregate-Scale Assessment of Pusa Decomposer-Assisted Residue Management on Soil Carbon Dynamics and Enzyme Activities in a Rice–Wheat System
摘要
Rice straw, a major by-product of cereal cultivation in the Indo-Gangetic Plains (IGP), is rich in lignocellulosic polymers that resist rapid microbial degradation. This often leads to residue accumulation and open-field burning, causing substantial soil organic carbon (SOC) losses and threatening soil health in the rice–wheat system (RWS). Although residue incorporation offers a sustainable alternative, its effectiveness is limited by slow straw decomposition. Therefore, this study evaluated the aggregate-scale effects of Pusa Decomposer-assisted residue management on carbon dynamics, aggregate-associated carbon, and enzyme activities in a rice–wheat system. A three-year field experiment was conducted under a randomized complete block design with five treatments: residue burning (RB), residue retention (RR), residue incorporation (RI), residue retention with Pusa Decomposer (RR + PD), and residue incorporation with Pusa Decomposer (RI + PD). The RI + PD treatment markedly enhanced soil aggregation, with macroaggregates increasing by 15.6% in the 0–5 cm depth and 11.8% in the 5–15 cm depth compared to RB. Water-soluble carbon (WSC) and permanganate-oxidizable carbon (KMnO4–C) increased by 92.4% and 81.4%, respectively, in the surface layer of bulk soil. In macroaggregates, Walkley–Black carbon (WBC) increased by 19.2% and total SOC rose by 14.9% under RI + PD compared to RB. Macroaggregate-associated carbon increased by 22.8% in the surface soil and 29.5% in the subsurface layer under RI + PD relative to RB. Microbial biomass carbon (MBC) improved by 158% in the 0–5 cm depth and 111% in the 5–15 cm depth, accompanied by 45–51% higher β-glucosidase and 50–79% higher dehydrogenase activity under RI + PD compared to RB. Principal component analysis revealed strong associations among carbon fractions, total organic carbon, and enzyme activities, reflecting enhanced microbial functioning and carbon transformation. These results indicate that decomposer-assisted residue incorporation enhances microbial-mediated carbon transformation and promotes aggregate-associated carbon stabilization beyond conventional residue incorporation. Overall, this study demonstrates that integrating Pusa Decomposer with residue incorporation effectively accelerates residue decomposition, enriches aggregate-associated carbon pools, and promotes soil health, thereby presenting a sustainable alternative to residue burning.