Evaluating cultivated land quality in loess hill and gully region and characterisation of topographic gradient using the minimum data set

Comprehensive scientific evaluation of the quality of cultivated land in loess hilly and gully region is of great significance in achieving the tripartite model of quantity, quality, and ecological protection of regional cultivated land and ensuring food security.This paper constructed the evaluation index system of cultivated land quality in loess hilly and gully region from multiple dimensions; and established the Minimum Data Set (MDS) index system based on multivariate statistical analysis methods. We took the Zichang City of Shaanxi Province as a case, using the subjective and objective methods to combine weighting, analyzing the spatial distribution characteristics of the cultivated land quality. Based on the topographic characteristics of the region, the method of topographical gradient analysis was introduced to probe into the features of topography gradient of cultivated land quality. The results showed that: ① The distribution of the cultivated land quality index (IFI) in Zichang City ranged from 0.15 to 0.90, with a mean value of 0.30. The cultivated land quality status of different townships had a large variation, with the overall level of the cultivated land quality index in Wayaobao Subdistrict Office, Yujiaping Township, and Anding Township being higher. ② The quality of cultivated land was mainly inferior, accounting for 41.57% of the area. Cultivated land quality grades showed significant spatial clustering characteristics, with low and inferior lands mainly distributed in the northern part of the county, and high and excellent lands mainly distributed in the south-west part of the county. From the perspective of townships, the area proportion of inferior land in each township ranged from 31.15% to 49.20%, while that of superior land ranges only from 0.71% to 6.23%. ③ The quality of cultivated land showed a significant topographic gradient, with the distribution index of inferior and low-grade land gradually increasing with the increase of the topographic gradient, while that of high, excellent and medium land gradually decreased with the increase of the topographic gradient. Taking the 3-level terrain gradient as the dividing line, the closer the terrain gradient was to level 1 or 6, the greater the difference in the distribution indices of the various cultivated land quality grades. Topographical factors played an important role in the distribution pattern of the quality of cultivated land, and the influence of topographical factors should be taken into full consideration when carrying out work related to the protection of cultivated land according to local conditions. This study improved the evaluation index system of cultivated land quality in loess hilly and gully region; and portrayed the relationship between topographic features and cultivated land quality more realistically and objectively. The results provided a decision-making basis for the improvement and protection of cultivated land quality in this region.