Green-depressing cropping system: A referential land use practice for fallow to ensure a harmonious human-land relationship in the farming-pastoral ecotone of northern China

The farming-pastoral ecotone of northern China (FPENC) is a fragile ecosystem that severely suffers from the acute contradiction between population growth and limited land resources. The Chinese government emphasized that rehabilitated agriculture, such as current government-led fallow, should be developed in the FPENC. However, what kind of farmland needs to lay fallow, how to manage the fields during fallow periods, and the duration of fallow periods are unclear. Fortunately, the green-depressing cropping system (GDCS) (Yaqing in Chinese Pinyin) that has existed for approximately 300 years also as a farmland use practice to reduce farmland use intensity and to recover soil property has something in common with fallow in the field selection and field management, and can serve as the reference for specific fallow policy. Therefore, we aimed to improve our limited understanding of the GDCS and provide recommendations for future fallow policies. Given this, an approach using satellite data to map the GDCS fields was explored, and this information can be combined with a questionnaire survey to help understand the current state of the GDCS in the FPENC. Then, the factors influencing farmers' willingness to adopt the GDCS in the FPENC were evaluated using a binary logistic regression model (BLR). The results indicated that the GDCS was still a widely distributed and common land use practice in the FPENC, and approximately 3.34 % and 2.31 % of the total arable land of Shangdu experienced the GDCS in 2019 and 2018, respectively. Furthermore, farmers in the Houshan area had a higher willingness to adopt the GDCS than farmers in the Qianshan area. More specifically, passive GDCS predominated as a suboptimal choice due to severe drought, while older farmers and agro-pastoral households had a higher willingness to adopt an active GDCS. Ultimately, the GDCS plays an important role in improving soil fertility and conserving soil water, leading to an increase of at least 50 % in crop yields in the year immediately following implementation. Finally, according to the current state of the GDCS and factor analysis, we concluded that the future fallow program in FPENC should be first performed in regions with high proportions of dryland and sloping fields, a small resident population, high levels of mechanization and high farmland transfer rates. Additionally, fallow by omitting a year of cropping is enough for farmland to recover, and different fallow subsidies are required to encourage farmers to implement this practice.