Effect of Coal Gasification Slag on Improving Physical Properties of Acid Soil

Coal gasification slag (CGS) is a coal-based solid waste formed by the transformation of inorganic mineral components and carbon components in raw coal into slag during coal gasification. To explore its influence on the physical characteristics of acid soil and study the influence mechanism on the water holding capacity of acid soil, the coarse and fine CGS were used as materials to mix with acid soil in different proportions. The volume weight, particle size composition, and water retention performance of the mixed soil were tested, and the changes of soil water characteristic curve were analysed. The results showed that, after mixing the acid soil with CGS, the particle size composition of acid soil was significantly improved, the sand content increased by 13.27–195.46%, the clay and silt content decreased by −2.14–38.62% and 3.22–40.06%, respectively; and the soil bulk density decreased significantly ( P < 0.05), with a decrease range of 3.38–28.12%. The soil texture also changed from silty loam to sandy loam, and the water retention performance showed an upward trend, which significantly affected the soil saturated water content, capillary water capacity and field water capacity, with an increase range of 2.87–38.09%, 1.73–27.92% and 4.18–22.27%, respectively. The Van Genuchten (VG) model could fit the soil water characteristic curve well, indicating that the water retention of acid soil was significantly improved by adding CGS. In conclusion, CGS could improve the water physical properties effectively, and improve the water retention and water holding properties of acid soil significantly. This feature is conducive to the environmentally friendly utilization of CGS to improve agricultural acid soil.