Evaluation of the impacts of coal mining on farmland quality in mine-agriculture regions in China

Abstract: Farmland quality refers to the ability of the land to perform agriculture functions, such as grain production, sustainable performance. The evaluation of farmland quality can include three aspects, background quality, economic quality and ecological environment quality. The indictor farmland quality provides the internal natural attributes, particularly on natural geographical conditions affected by social and economic input. Specifically, the "mining-agriculture" combined method can be widely engaged in agricultural production on the ground, while coal mining underground in Shanxi Province, China. Coal mining has caused serious damage to the farmland, where the quality of cultivated land has deteriorated, and thereby posed great threat on food security and social stability. Therefore, it is necessary to systematically evaluate the impact of coal mining on the quality of farmland in the mine-agricultural complex region, as well for the formulation of regional land reclamation plans. Taking the Changhe river basin in Zezhou County, Shanxi Province as the research area, four indexes were selected to characterize overall farmland quality, including natural quality of farmland, agricultural production conditions, location conditions, and farmland environmental conditions, according to the national standard "Regulations on Agricultural Land Grading and Classification". A specific index system was established to spatially visualize four indexes using the geographic information technology, ArcGIS. A multi-factor weighted algorithm was used to analyze the spatial distribution of each index, and to obtain comprehensive evaluation for the quality of farmland, particularly on coal mining subsidence areas. The results show that the constructed index system of farmland quality can be suitable for the "mine-agriculture" compound regions, reflecting the farmland status of the target areas. The evaluation scores of farmland natural quality, agricultural production conditions, location conditions, and farmland eco-environmental conditions were low in the undisturbed area of coal mining. The farmland quality within the boundary of the coal mine field (average 0.37) was much lower than that of non-mining farmland (average 0.55). It infers that coal mining can affect independent indicators, such as natural quality, economic quality and farmland environmental quality, and ultimately lead to a serious decline in the fertility of farmland at the regional level. The main reason is that the underground coal mining can destroy the topography on the ground, thereby result in soil nutrients loss, broken plots, ground subsidence of roads, and the discharge of mining pollutants at high levels of environmental pollution in local farmland. This finding can provide a theoretical basis to formulate a scientific and rational land-rehabilitation plan for the mine-agricultural complex regions, and comprehensive land improvement plans.