<b>Straw returning combined with controlled-release nitrogen fertilizers promote organic carbon sequestration by regulating microbial communities and metabolic limitation.</b>

Soil organic carbon (SOC) is a key component of the soil carbon cycle and an essential indicator for sustainable agriculture development and climate change mitigation. However, it remains unclear how long-term straw return and nitrogen (N) fertilizer application affect soil microbial communities and metabolic limitations and how both contribute to SOC sequestration. Based on this, we conducted a long-term field experiment with six treatments: no N fertilizer, regular N fertilizer, and controlled-release N fertilizer treatments under straw return and no straw return conditions, respectively, with each treatment replicated three times.土壤有机碳（Soil Organic Carbon, SOC）是土壤碳循环的核心组成部分，亦是可持续农业发展与气候变化减缓的关键指示指标。然而，长期秸秆还田与氮（N）肥施用如何影响土壤微生物群落及代谢限制，且二者如何共同促进土壤有机碳固存，目前仍尚不明确。基于此，我们开展了一项长期田间试验，共设置6组处理：分别在秸秆还田与无秸秆还田条件下，设置不施氮肥、常规氮肥及控释氮肥三种处理，每组处理均重复三次。