Background  The protection and restoration of the ecological environment has attracted the world's attentions and became the focus of the research field. The researchers have been focusing on the improvement of the physical and chemical properties of mine spoil by using organic fertilizer, water retaining agent, garden waste, sludge, and other materials. However, the influences of different particle size and amount of spoil on soil moisture and plant growth have been ignored, thus we conducted this research to understand the amelioration effects of dress-soil at varied ratio on limestone spoil at different particle sizes.

Methods  We chose limestone quarry spoil from Fangshan District of Beijing as research materials, and then sieved it into 20-40 mm, 10-20 mm, 2-10 mm and < 2 mm. For simulating the particle size distribution of actual spoil, we used the spoil of above 4 particle sizes to create 12 kinds of spoil by combining them in varied ratios, and then mixed the dress-soil in the proportion of 0%, 20%, 40%, 60%, 80% and 100%. We selected the pot experiment, and sowed the Festuca elata 100 seeds in mixed spoil per pot, and measured the survival rate, height, biomass and root-shoot ratio in the following two years. For comparing the bulk density, porosity, capillary water holding capacity and maximum water holding capacity of the mixed spoil before and after the pot experiment, we took and tested the samples by ring knife method. The experiment data was processed by Excel2016 and SPSS19.0 software for Pearson correlation analysis.

Results  The influence of dress-soil improvement of limestone spoil reflected certain irrigation sedimentation process, and adding and mixing dress-soil effectively improved spoil water holding capacity and subsequently improved the growth of tall fescue. The spoil water properties correlation order of different particle size by the amount of dress-soil addition was 20-40 mm < 10-20 mm < 2 mm < 2-10 mm, and the correlation order of tall fescue growth was 2 mm < 2-10 mm < 10-20 mm < 20-40 mm. The optimal dress-soil ratio for the spoil of < 2 mm and 2-10 mm particle sizes was 40%, and was 60% for 10-20 mm and 20-40 mm particle size of spoil. Adding more than the optimal ratio of dress-soil caused little more amelioration effects of limestone spoil, and economic and ecological benefits were low.

Conclusions  By this study we obtained the soil water properties and growth of tall fescue in different particle size limestone spoil mixed with dress-soil, the research methods and results may provide a reference for mine spoil utilization and ecological restoration. We should focus on the influence in the ameliorating process of different rock types, mineral composition, weathering degree and salt content in the further research on the improvement of mine waste rocks.