In order to cope with the ecological pressure caused by the uncontrolled expansion of cultivated land in arid areas and ensure regional food security, the implementation of a cultivated land fallowing system has become an effective way to restore the ecology, alleviate the pressure on cultivated land, and increase productivity. In view of this, this paper takes the Tarim River Basin, located in the arid zone of China’s agricultural continent, as the research object. Using a land use transfer matrix and a gravity center migration model, the paper analyzes the spatiotemporal characteristics of cultivated land expansion in the Tarim River Basin from 2000 to 2020. Through remote sensing and the integration of multi-source data, the paper constructs an arable land fallow urgency index (SILF) from multiple dimensions such as human activity intensity, ecological vulnerability, output value, water resources status, and terrain conditions. The research results show that (1) cultivated land in the Tarim River Basin expanded by 15,665.133 km² in general, which is manifested by spreading around based on existing cultivated land, mainly from the conversion of grassland and unused land; the center of gravity of cultivated land moved 37.833 km to the northeast and 7.257 km to the southwest first. (2) The area of not urgently fallow (NUF) in the watershed showed an overall downward trend, decreasing by 10%, while the area of very urgently fallow (VUF) increased by 16%. VUF is mainly distributed in the marginal areas of cultivated land close to the desert and is gradually expanding into the interior of cultivated land. (3) The overall ecological environment of cultivated land in the watershed is showing a deteriorating trend, and the deterioration is gradually spreading from the edge of the cultivated land to the interior. (4) There are significant differences in the SILF values of different land use types after conversion to cultivated land. The urgency of fallowing cultivated land converted from unused land is the highest, followed by grassland, forest land, water bodies, and construction land. The expanded cultivated land has a higher SILF value than the original cultivated land. The research results can provide insights into regional land resource management, the formulation of cultivated land protection policies, and the ecological restoration of cultivated land.

The withdrawal of cultivated land policy is not only an important task to promote cultivated land rest and alleviate the contradiction between supply and demand of water resources in arid areas, but also an important way to realize the sustainable development of agriculture and social economy. This study adopted the minimum per capita area method, ESPR (Exposure-Sensitivity-Pressure-Response) vulnerability assessment model, grey prediction model, and GIS spatial analysis. Furthermore, based on the characteristics of water resource constraints in the arid zone, Manas County was used as the study area. By exploring and analyzing the area of land retreat, through identifying its occurrence and position, the spatial zoning layout of land retreat can be realized to guarantee the effective implementation of water retreat and reduction. The following points were noted from the results: (1) the upper and lower limits of the area of receding land in Manas County were measured using the minimum per capita area method and the principle of balancing water supply and demand. The receding land in Manas County measured 16,493.68–20,749.90 hm², which accounted for 24.31–30.58% of the total area of cultivated land. (2) The results obtained from constructing the ESPR vulnerability assessment model, used to assess the vulnerability of cultivated land in Manas County, showed that the overall vulnerability of cultivated land in Manas County was high, with 94.74% of the county’s cultivated land being moderately vulnerable or worse, which necessitates the optimization of land use. (3) The area of cultivated land withdrawal under the water resource constraint was used as a constraint for the withdrawal of cultivated land. Based on the evaluation of the vulnerability of cultivated land, with the results arranged from small to large, it was concluded that the area of cultivated land withdrawal in Manas County could reach up to 16,787.34 hm². There are four types of cultivated land withdrawals: desertified withdrawal, saline withdrawal, groundwater overexploitation withdrawal, and soil contamination withdrawal. The results of this study can provide a reference for Manas County to scientifically formulate a reasonable and orderly withdrawal system of farmland to reduce water use.