Coupling coordination analysis of the quality evaluation of cultivated land and soil erosion in typical black soil areas using TOPSIS method

The black soil area in northeast China is an important food producing area. The evaluation of cultivated land quality in the black soil area is the basis for mastering the quality status of cultivated land and promoting the sustainable use of cultivated land. In addition, it is important to clarify the soil erosion in black soil areas and explore the degree of coupled and coordinated development of cultivated land quality and soil erosion to maintain healthy agricultural development and national food production security. Based on this, this study took Nenjiang city, a typical black soil area in China as the research area. A comprehensive evaluation of the cultivated land quality in Nenjiang City was made based on technique for order preference by similarity to an ideal solution (TOPSIS) model by constructing five dimensional indices: geoscience characteristic index, property index, soil health index, infrastructure construction index, vegetation growth index. The RUSLE model was used to assess the soil erosion in the study area, the coupled coordination degree model was used to explore the degree of coupled and coordinated development of cultivated land quality and soil erosion, and further to clarify the main influencing factors limiting the cultivated quality. The results showed that: 1) the quality index of cultivated land in Nenjiang City ranged from 0.26 to 0.67, and the quality level of cultivated land varied greatly in different regions. The quality of cultivated land was mainly "intermediate grade" cultivated land, which accounted for 29.6% of the area. High grade cultivated land accounts for less, and the cultivated land quality needs to be further improved to maintain the safety of agricultural production. 2) The results of diagnostic analysis of barrier factors showed that the barrier degree of soil pH, drainage capacity, irrigation capacity, plot contiguity and relative vegetation index in the index layer was high, all exceeding 60%, which were the main reasons limiting the cultivated land quality. The highest degree of infrastructure development index barriers for cultivated land in the criterion layer had a significant impact on the cultivated land quality. 3) The soil erosion modulus of Nenjiang City was distributed between 0 and 30.7 t/(hm²·a). The area of slight erosion was the largest, accounting for 75.45% of the total study area, and the area of heavy erosion was the smallest, accounting for less than 1% of the study area. From the perspective of spatial distribution, the degree of erosion in the southwestern region was relatively weak, and the more serious erosion areas were mainly distributed in the northern, central and eastern areas of Nenjiang City. 4) The coupling coordination degree of soil erosion system and cultivated land quality ranged from 0.25 to 0.99, and there was some variability in the spatial distribution of the coupling coordination degree values. However, most of the spatial evaluation units had the coupling coordination degree values greater than 0.7, and overall soil erosion and cultivated land quality were in a good state of synergistic development. This study can provide a new perspective for the comprehensive and integrated evaluation of cultivated land quality assessment, and provide a theoretical basis and scientific reference for the sustainable development management of cultivated land in black soil areas and the formulation of related land use policies.