Abstract:
Previous assessments of soil quality changes related to the transfer of soil in and out of cultivated land have seldom accounted for the physical and chemical properties of the soil. The Ili River Basin is an important agricultural and husbandry base in Xinjiang that has undergone significant changes in its natural environment and socioeconomic conditions over the past 30 years. This study used a 30-meter resolution dataset of China’s multi-year land cover to obtain the spatial distribution data of cultivated land in the Ili River Basin from 1990 to 2020, exploring the changes in the quantity of cultivated land as well as the source and distribution of transferred cultivated land. Based on the DEM data and basic attribute dataset of the China high-resolution national soil information grid, we calculated Cohen’s D values to compare the differences in elevation, slope, organic carbon content, total phosphorus content, total nitrogen content, sand content, and pH between transferred-in and transferred-out cultivated land and compared these with the data from the seven major agricultural regions of China. Compared with 1990, the area of cultivated land in the Ili River Basin increased from 6 196.80 km
2 to 8 606.51 km
2 by 2020. The transferred cultivated land was mainly high-elevation grassland concentrated along the banks of the rivers, which was mainly related to improved irrigation and water diversion capacities in the basin. From 1990 to 2020, transferred-in cultivated land increased significantly in elevation compared to transferred-out cultivated land, whereas the slope showed only a slight increase (Cohen’s D values of 0.851 and 0.276, respectively). Organic carbon content and total nitrogen content increased moderately and slightly, respectively, while the changes in total phosphorus content, sand content, and pH were very small (Cohen’s D values of 0.558, 0.308, −0.116, 0.081, and 0.001, respectively). This indicates that the soil quality of the transferred cultivated land in the Ili River Basin is fairly good, which is different from that in Xinjiang and the seven agricultural regions of China. A large area of arable grassland is available for future cultivation in Ili. However, to ensure the balanced development of agriculture and husbandry and to reduce ecological risks, future overcultivation of grasslands should be limited, especially in ecologically vulnerable high-altitude areas (such as those above 2,000 m) and steep slopes, which should receive special attention.