Restoring subsided coal mined land to farmland using optimized placement of Yellow River sediment to amend soil

Underground coal mining causes land subsidence and large areas of cultivated land are destroyed. The Yellow River interlayer filling reclamation technology is a powerful way to restore cultivated land. Understanding the mechanism of action of interlayers in reconstructed soil filled with Yellow River sediment is essential to achieving sustainable land management in the Yellow River regions. Column experiments and field experiments were conducted to explore optimum interlayer placement in reconstructed soil with Yellow River sediment for restoring subsided land. Our findings show that the inclusion of interlayers in the sediment reduced water leakage and moisture evaporation and improved the water-holding capacity of the material in comparison to a conventional reconstructed soil profile (CK2). The optimal profile with the highest water-holding capacity was constructed using two 30 cm thick interlayers (T6). In comparison to CK2, the migration rate of the wetting front decreases by 32.16%, the cumulative evaporation decreases by 16.29%, the volumetric water content of the filling layer (θ_fl) increases by 121.56%, and the water-holding coefficient (C_WR) increases by 59.47%. The same trend is also demonstrated by field experiments. The wheat and maize yields of T6 improved 45.85% and 60.69%, respectively, as compared with CK2, that more closely resembles undisturbed farmland (CK1). This study provides a valuable framework for subsided land reclamation regarding the method of placing interlayers into Yellow River sediment for enhancing water retention and productivity.