Soil and crop management to promote formation of stable soil organic matter

土壤中三分之二的陆地有机碳(C)以土壤有机质(SOM)的形式存在，这一碳库的大小是大气或活植物生物量的两倍多。SOM对于支持植物、动物和微生物的生命至关重要，因为它在增强调节土壤质量的物理和化学性质方面发挥了作用。这包括保留植物的基本养分，提高水分利用效率，促进聚集，从而减少侵蚀，并对土壤肥力作出直接贡献。与当地土壤耕作相比，农业集约化土壤耕作和一年生粮食种植使土壤有机质水平下降了30-50%。土壤管理(耕作措施)和种植制度影响植物残渣投入的质量和数量，以及植物残渣腐烂和土壤有机质周转的速度。尽管占全球有机碳约10%的农业土壤是大气二氧化碳排放的重要贡献者，但它们有可能成为全球大气二氧化碳C的主要储存库，在那里可以将其作为数百至数千年的稳定腐殖质进行封存。正在积极推动采用适当的栽培和管理做法，包括复杂的轮作和保护性耕作(减耕或免耕)制度，以及归还作物残留物和有机废物，以保护和提高土壤有机质水平。近年来，农业土壤有机质组分的定量和定性测量因其在减缓气候变化方面的潜力而成为一个主要的研究热点。

Two-thirds of the terrestrial organic carbon (C) in soil is contained as soil organic matter (SOM), a pool of C more than twice the size of that in the atmosphere or in the living plant biomass. SOM is critical for supporting plant, animal and microbial life because of its role in enhancing the physical and chemical properties that regulate soil quality. This includes retention of essential plant nutrients and increasing water-use efficiency, promoting aggregation thereby reducing erosion, and its direct contribution to soil fertility. Intensive soil cultivation for agriculture combined with the growing of annual crops for food production have depleted SOM levels by 30-50% compared to that in their native counterparts. Soil management (tillage practices) and cropping systems influence the quality and quantity of plant residue inputs, and the rates of plant residue decay and SOM turnover. Although agricultural soils, which account for ~10% of global organic C, have been a significant contributor to atmospheric CO2 emissions, they have the potential to be a major global reservoir for atmospheric carbon dioxide C where it can be sequestered as stable humus that is hundreds to thousands of years old. Adoption of appropriate cultural and management practices, including complex crop rotation and conservation tillage (reduced or no-till) systems, and returning crop residues and organic wastes are being actively promoted to protect and enhance SOM levels. Recently quantitative and qualitative measurements of the components of SOM in agricultural soils have become a major research focus due to their potential for mitigating climate change.