Straw Incorporation Strategies Regulate Detritusphere Organic Carbon and Nutrient Accumulation

ABSTRACT Straw incorporation is a widely adopted agricultural practice, with the detritusphere formed through straw‐soil interactions serving as a critical hotspot for nutrient cycling and soil organic carbon (SOC) accumulation in farmland soils. However, the detritusphere has been largely overlooked, and its relationship to straw component release and responses to management practices remains poorly understood. This study investigated the mechanisms of straw component release, nutrient cycling, and SOC accumulation in the detritusphere under four straw management regimes: straw mulch (SM), surface incorporation (SI), deep‐ploughed straw incorporation (DP‐SI), and deep‐injection straw incorporation (DI‐SI). Incorporated straw sequentially provides carbon sources to the detritusphere in the order of cellulose, hemicellulose, and lignin. After one year, the detritusphere under DI‐SI and SM retained higher straw residues, at 15.7% and 18.0%, respectively, and exhibited higher soil nutrients and SOC content, with an average increase of 24.5% and 28.4% compared to the bulk soil. Subsoil straw incorporation (DP‐SI and DI‐SI) resulted in a 2‐ to 7‐fold increase in nutrient availability, microbial biomass carbon, and enzyme activities in the detritusphere than topsoil straw incorporation (SM and SI). In the detritusphere, the transition of carbon sources from easily decomposable to recalcitrant substrates led to a shift in SOC dynamics, with net accumulation shifting to net loss at a critical threshold of ~71% straw decomposition. In conclusion, the biochemical characteristics of the detritusphere are closely linked to the release and retention of straw components, which are strongly influenced by straw incorporation strategies. DI‐SI retained more straw residues in the detritusphere and demonstrated substantial potential for improving soil nutrient cycling, enzyme activity, and SOC accumulation.