Improving Saline-Alkaline Soil and Ryegrass Growth with Coal Gangue Treatments.

Soil covering is a soil management technique used to address issues such as high alkalinity, nutrient deficiency, and a low soil and water-holding capacity in saline-alkali lands. Coal gangue, a solid waste generated from coal mining, contains nutrients and trace elements comparable to those in soil, making it a promising covering material. This study investigates the effects and mechanisms of coal gangue coverage on the physicochemical properties of soil, enzyme activity, and the growth of ryegrass. The experimental treatments comprised (1) three coal gangue particle sizes (0-0.5 cm, 0.5-1 cm, and 1-2 cm) and (2) three coverage thicknesses (4 cm, 8 cm, and 12 cm). The results show that with particle sizes of 0-1 cm and cover thicknesses of 8-12 cm, the saturated water content of the soil increased by 11.1% to 17.23%, the content of organic matter rose by 4.99 to 13.64 mg/kg, the total nitrogen increased by 0.07 to 0.12 mg/kg, and the urease activity increased by 0.56 to 0.64 μg/(d·g). Our analyses indicated that an improvement in soil porosity, a reduction in pH, and an increase in urease, organic matter, and total nitrogen collectively promoted ryegrass growth, with similar impacts. Among the treatments, coverage with 12 cm of coal gangue with a size of 0.5-1 cm produced the best results, increasing the ryegrass height by 16.24 cm, primarily due to a high level of soil porosity and elevated urease activity. In conclusion, coal gangue coverage significantly improves the properties of soil, enhances enzyme activity, and promotes ryegrass growth.