Development of soil physicochemical properties of reclaimed croplands in a large opencast mining area on the Loess Plateau

In this study, we collected soils from 11 plots of the reclaimed cropland at a large-scale opencast coal mining area, analysed their profile properties and compared these properties with the properties of undamaged and unreclaimed croplands. These properties were compared using comparative analysis, variance analysis, correlation analysis and principal component analysis to reveal the underlying rules of variation with reclamation years. The results indicate that the soil profile properties of the reclaimed cropland vary significantly with differences in depth, particularly at depths of 30, 40 and 50 cm. In addition to soil organic matter and soil total K, most significant differences among the three types of croplands were soil fertility followed by soil physical indicators. There were positive correlations between soil bulk density and soil pH (p<0.01), between soil field moisture capacity and total phosphorus (p<0.05), between soil organic matter and total nitrogen (p<0.01), between soil organic matter and soil available K (p<0.01) and between soil organic matter and soil total phosphorus (p<0.01). The primary physicochemical factors affecting the properties of soil in reclamation croplands were soil physical and chemical indexes for those croplands that have been reclaimed for 2 years and organic matter and soil nutrients for those croplands that have been reclaimed for 13 years and 18 years, as well as undamaged cropland. The distribution of the physical soil profile and chemical properties of the croplands that have been reclaimed for 13 and 18 years were highly consistent with the properties of the undamaged croplands.