Responses and Feedbacks of Particulate Organic Matter to Straw Deep Incorporation in Northeast China

Particulate organic matter (POM) represents the most active carbon (C) pool in agroecosystems. However, the contribution of POM to soil C sequestration under different straw return methods remains unclear, owing to its substantial interactions with soil physicochemical properties and microbial communities. This review gives a brief overview of the biochemical characteristics and analytical techniques of POM and then focuses on the actuation mechanisms regulating its spatiotemporal dynamics. It also discusses the application of POM management strategies, particularly through straw deep incorporation, to increase soil C stock and sequestration potential. In contrast to straw mulching and shallow incorporation, which concentrate C in the topsoil layer prone to C saturation, deep incorporation introduces fresh straw-derived C into the subsoil horizons. This process reshapes the pore networks by increasing the abundance of pores in the 30–90 µm range with high connectivity, and induces changes in soil aggregates, microbial communities, and enzyme activities. In the low-oxygen and thermally buffered environment of the subsoil, deep incorporation substantially increases POM-derived C and enhances C sequestration efficiency by 15%–30% compared with the traditional practices. Spatial optimization framework for agricultural POM management presented here provides a theoretical basis for enhancing C sequestration and improving ecosystem services in Mollisols of Northeast China.