<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.