No abstract

Objective: The evaluation of cultivated land quality from the regional perspective and the clear level and change in cultivated land quality in the whole region can better guide the construction of cultivated land quality, carry out scientific optimization allocation, improve grain production capacity, and promote the sustainable use of cultivated land. Research methods: The utilization of local resources and natural conditions were comprehensively considered, and the evaluation was carried out from the four dimensions of ecology, quantity, spatial structure and scale to comprehensively reflect the level of regional cultivated land utilization. Results: (1) The cultivated land quality level of the Horqin Zuoyihou Banner is low, and the pressure of regional water resources is great. Some cultivated land is located in the area with poor natural conditions, and there are many thin and narrow cultivated areas of land. The area of cultivated land that can be carried by regional water resources under current irrigation is 184,492.17 hm2, and that under water-saving irrigation is 259,703.72 hm2, which are lower than the current cultivated land areas. (2) During the study period, the total amount and spatial distribution of cultivated land changed greatly, and there were good natural conditions and utilization conditions of newly added cultivated land, but the quality of cultivated land from the regional perspective showed a downward trend. The dynamic attitude of cultivated land change was 0.99%. (3) According to the evaluation results, the cultivated land was divided into the following four categories: priority protection type, optimization and coordination type, gradual conversion type and priority conversion type, which accounted for 34.18%, 30.59%, 28.83% and 6.40% of the total cultivated land area, respectively. Conclusions: There is a sharp contradiction between the supply and demand of water resources, and the quality of cultivated land in the region is low and shows a downward trend, which is not conducive to the sustainable use of regional land resources. In this regard, the Horqin Zuoyihou Banner should actively curb the growth of cultivated land, develop water-saving irrigation processes, strengthen ecological environment protection, and systematically optimize the layout of cultivated land on the premise of ensuring ecological security according to the actual conditions of different regions.

Under water resource and terrain constraints, a certain scale threshold of irrigated and rainfed agricultural areas exists in semi-arid sandy areas. If this threshold is exceeded, water and soil resources will be unbalanced, and the ecological environment will deteriorate. Accurate assessment of the suitable scale of cultivated land in semi-arid sandy areas is of great significance for sustainable utilization of cultivated land resources and regional ecological security. Most existing research methods are based on water resource constraints and rarely consider terrain factors. Therefore, based on the principle of water balance and with the Horqin Left Wing Rear Banner as the research area, this study adopted a multi-objective fuzzy optimization model and relative terrain index analysis method to explore the appropriate spatial ratio of irrigation and rainfed agriculture. The results show that the area of irrigated agriculture in the study area is 77,700 hm2, and the appropriate scale is 91,700 hm2. The current area of dry farming is 184,600 hm2, and the suitable scale is 117,100 hm2. The results also show that the utilization efficiency of water and soil resources in irrigated agriculture was not optimal, rainfed agriculture exceeded its suitable scale, and water and soil resources were seriously unbalanced. However, the region of cultivated land that exceeds the appropriate scale is mostly located in an area with poor terrain, less precipitation, and other unsuitable conditions for cultivation, which is prone to abandonment, resulting in deterioration of the ecological environment. Therefore, the spatial layout of agricultural land use in the study area should be adapted to local conditions, and the water-saving structure of irrigated agriculture should be optimized to achieve the maximum comprehensive benefits. Dry farming should be controlled on a reasonable scale, and the part exceeding the appropriate scale should be returned to grassland to ensure sustainable development.

The sustainable development and utilization of sandy areas in arid and semiarid regions is of strategic importance to ensure both food and ecological security. The unique geographical environment of these areas and uncontrolled exploitation by farmers lead to large amounts of fragmented cropland. Despite government management, the quantity and distribution of these fragmented croplands is unknown, and accurate identification of the region’s fragmented croplands can provide data to support the sustainable use of sandy areas. We propose a method for identifying fragmented cropland based on scale transformation. Small-scale fragmented cropland is approximately represented at larger scales, so we apply small-scale high-resolution remote sensing images to identify features and obtain information at a large scale, i.e., the ratio of fragmented cropland area. By correcting the cropland areas identified from low-resolution remote sensing images and using them as the basis for the resulting calculation, more accurate identification can be 1 at a large scale. In this study, this method was applied based on remote sensing images with 0.54 and 30 m resolutions that were acquired during the same period, using Horqin Zuoyihou Banner as the study area. The results showed that (1) there was 13,637.08 hm2 of fragmented cropland in Horqin Zuoyihou Banner due to precipitation and terrain topography, mainly in the central and western regions and 2) identification at the sample point scale and plot scale were positively correlated in area and showed a consistent distribution. Therefore, accurate and efficient identification of fragmented cropland can be achieved through scale transformation.