The Effect of Thickness of Covering Soil on Soil Water Retention and Crop Growth in Land Reclamation Filled with Fly Ash: Evidence from GPR and UAV Investigation

Rapid, accurate, and non-destructive monitoring after land reclamation is the basis of and key to realizing land restoration evaluation, as well as land use direction decision-making and improvement. However, the biggest problem with the filling reclamation method is the poor soil water retention caused by the insufficient thickness of covering soil (TCS), which results in the loss of soil nutrients. In addition, the cost of filling reclamation has also increased due to the excessive TCS. In this study, multi-source remote sensing data acquisition methods were used to assess the impacts of the TCS of the filling reclamation method on soil water retention and crop growth (CG). We found that as the TCS increases, the overall trend of the CG gradually increases, and the overall trend of the soil water content slowly increases. However, considering the huge economic costs and the cost of soil sources, we suggest that the optimal TCS for the filling reclamation method should be controlled within 40-50 cm. The results of this study provide a reference for the use of multi-source remote sensing technology for rapid evaluation of the restoration effects of reclaimed areas and for the rational utilization of coal chemical wastes.