<p>Soil conservation practices such as no-till and straw mulching have been practised worldwide, but they frequently show low potential to increase organic carbon and crop grain production, especially in rice paddy systems. Here a ditch-buried straw return technique is proposed to co-enhance soil carbon and crop yield in paddy systems through injection of straw into the subsoil. This technique can protect most of the surface soil and disturb only 10% of the whole field through deep tillage. A 15-year ditch-buried straw return experiment in rice–wheat cropping has shown that compared to the dominant rotary-tillage straw return management, grain yield was increased under ditch-buried straw return by 15% without any additional fertilization inputs. Ditch-buried straw return also increased soil organic carbon stocks at 0–40 cm depth by 46% (17.2 Mg ha⁻¹) mainly through the enhanced conversion of straw-derived carbon into mineral-associated fungal necromass. Overall, ditch-buried straw return decreased net CO₂ equivalent emissions by 34% and increased net economic benefits by 18%. Joint enhancements of soil organic carbon and crop yield under ditch-buried straw return were further validated using meta-analysis around China. We conclude that ditch-buried straw return may work as an effective approach for subsoil management.</p>