华北平原保护性耕作禾豆模式土壤固碳效应及其稳定机制的研究

发展禾豆模式有利于华北平原地力培肥，对该地区农业可持续发展具有重要意义。保护性耕作是气候智慧型的主要技术之一，其固碳机制与潜力是当前重要的研究内容。但不同种植模式，特别是禾豆模式下保护性耕作碳库动态的研究还十分薄弱。因此，探明保护性耕作禾豆模式土壤固碳效应及其稳定机制，对于优化碳库管理策略至关重要。基于此，本项目采用田间试验与室内培养试验相结合的方法，重点比较不同耕作方式（免耕和旋耕）在麦-玉两熟和麦-豆两熟模式下土壤有机碳库及有机碳组分构成的差异，阐明土壤碳库与全氮、关键理化性状、作物根系及气象因子等的动态关系；明确土壤有机碳不同组分矿化规律及产物的变化；系统研究不同含氮物质投入对土壤碳矿化的影响，探明豆科作物固氮与土壤固碳的关系，揭示豆科作物对保护性耕作土壤固碳及其稳定机制的影响，以期为华北平原进一步优化保护性耕作技术，构建“用养结合”型农作模式提供理论支撑和参考。

Adopting cereal-legume rotation will enhance soil fertility in the North China Plain, which is essential to the sustainability of regional agriculture. As one of the main climate-smart technologies, the mechanism and potential of conservation tillage (CT) to sequester soil organic carbon (SOC) are important issues in recent research. However, in-depth studies are needed to reveal effects of different cropping systems, especially of cereal-legume rotation, on SOC dynamics under CT. Thus, addressing the mechanisms on SOC sequestration and stability under CT with cereal-legume rotation is vital for optimizing the strategies on soil carbon management. Based on field and laboratory incubation experiments, this program was designed to assess the differences in SOC pool and its fractions between wheat-maize and wheat-soybean systems under tillage practices (no-till and rotary tillage). The objectives were also to determine the relationships between SOC and soil total nitrogen, key soil properties, crop root production, and/or climatic conditions; clarify the mineralization and the by-products of SOC and its fractions; evaluate the effects of adding nitrogenous substance on SOC mineralization; and reveal the relationship between biological nitrogen fixation and SOC sequestration. By explaining the effect mechanisms of legume crop on SOC sequestration and its stability under CT, this program can provide theoretical supports and examples for optimization in adopting CT practices and development of a “balance in usage and maintenance” farming system in this region.