Objective The aims were to investigate the effects of different straw mulching amounts on soil carbon sequestration potential and carbon for fertilizer cultivation under no-tillage conditions, and to provide a theoretical basis for optimizing the management mode of farmland straw in the Mollisols area of Northeast China.

Method Mollisols was selected as the research object, relying on the Research and Development Experimental Base of Conservation Tillage of Institute of Applied Ecology, Chinese Academy of Sciences. No-tillage + no straw mulching (NT-0) was used as the control, three treatments of no-tillage + low-amount straw mulching (NT-1/3), no-tillage + medium-amount straw mulching (NT-2/3) and no-tillage + high-amount straw mulching (NT-3/3),the experiment lasted for 9 years that the soil nutrient content, soil organic carbon (SOC) content and soil organic carbon storage (SOC_s), dissolved organic carbon (DOC) and dissolved organic carbon efficiency (DE), oxidative stability coefficient (K_os) were set to analyze, and the carbon pool management index (CPMI) was also calculated and analyzed by using the carbon lability (CL) and carbon lability index (CLI) of different soil layers (0 - 5 cm, 5 - 10 cm, 10 - 20 cm, and 20 - 40 cm).

Result ① Compared with NT-0, the SOC content in the top 0 - 5 cm with NT-2/3 and NT-3/3 straw mulching treatments significantly increased by 22.31% and 29.37%. But only the NT-3/3 treatment significantly increased the SOC_s in the 0 - 40 cm. ② Compared with NT-0, none of the treatments with different amounts of straw mulching significantly affected the SOC content of 0 - 20 cm, but the NT-1/3 treatment significantly decreased the DOC content of 20 - 40 cm. DE was significantly increased by 25.29% and K_os was significantly decreased by 20.56% in 5 - 10 cm under the NT-2/3 treatment. ③ Compared with NT-0, the NT-2/3 and NT-3/3 straw mulching treatments significantly increased CL and CLI in the subsurface 5 - 10 cm. Compared to the low-amount, CPMI was significantly increased by 28.50% and 22.50% in the NT-2/3 and NT-3/3 straw mulching treatments. In addition, CPMI was significantly and positively correlated with total phosphorus in soil nutrients.

Conclusion In the process of agricultural production, if considering to promote the availability and stability of SOC, the medium straw mulching is the best choice for returning to field. While if the enhancement of SOC_s accumulation and carbon sequestration potential is considered, the high-amount straw mulching is more effective. This provides a theoretical basis for optimizing the straw management mode and the sustainable development of agriculture in the Mollisols area of Northeast China.