Abstract:To investigate the effects of coal gangue on revegetation and microbial properties of an alkali-saline soil, coal gangues with different application rates (0, 10%, 20%, 30%, 40%, 50%) and different particle sizes (small-size of <1 mm, medium-size of 1~5 mm, large-size of >5 mm, mixed-size) were applied to an alkali-saline soil. Then the alfalfa pot experiment was conducted to determine the height and biomass of alfalfa and soil microbial biomass and enzymes activities. The results showed that soil microbial biomass C and N, activities of urease, catalase and dehydrogenase, as well as plant height and biomass of alfalfa all increased first and then decreased with the increase of coal gangue application rates. As for the mixed-size, small-size, medium-size, and large-size coal gangue treatments, the above soil properties reached their peaks when the application rates were 20%, 20%, 30%, and 40%, respectively. Among them, coal gangue application rate of 20% with mixed partical size gave the best improvement effect on revegetation of alkali-saline soil. The plant height and fresh weight of alfalfa significantly were increased by 34.86% and 45.28%, respectively. Therefore, the application of coal gangue could improve the ecological quality of saline-alkali soil. The coal gangue with mixed particle size and 20% application rate could be used as an effective amendment for the revegetation of alkali-saline soil.