Soil organic carbon (SOC) is the key component of the C cycle in the terrestrial ecosystem. The input of soil organic matter to soil, SOC accumulation, and CO_2 emission are the main components of soil C cycle. It is a win-win strategy to increase SOC accumulation and reduce CO_2 emission for sustainable agricultural development and the decreased CO_2 concentration. The Loess Plateau, one of the areas with the most serious soil erosion in the word, is a typical rainfed agricultural area and an ecological fr...