Experimental study of planting substrate mixed with coal gangue  and municipal sludge

Coal gangue and municipal sludge, which are both wastes, have certain complementarities in nature, and there are still few studies on the synergistic utilization of these two wastes. In order to explore the feasibility of the preparation of plant substrate by mixing coal gangue and municipal sludge, and to obtain specific and efficient utilization methods, different volume proportions (5 levels：50%，60%，70%，80%，90%) and different particle sizes (3 levels：coal gangue≤2 mesh，≤4 mesh，≤8 mesh) of coal were mixed with municipal sludge to make planting substrate and planted with tall Festuca arundinacea L. in sandy soil. The effects of co-disposal of coal gangue and municipal sludge were evaluated by measuring and analyzing the contents of heavy metals and nutrient elements in soil and the germination rate and biomass accumulation of plants. The results show that sludge is the main nutrient source of plant growth substrate, especially it can provide a lot of phosphorus element. Coal gangue itself contains considerable nutrients and can adjust the physical structure of plant substrate to make it more suitable for difficult sites. Compared with the other particle size groups, when the particle size of coal gangue is less than or equal to 8 mesh, the content of organic matter in soil is significantly increased (P<0.01);. both the volume proportion and particle size of gangue have significant effects on biomass accumulation of high fescue，and there is an obvious interaction between the two variables. Comprehensive consideration shows that when the volume ratio of coal gangue and municipal sludge is 1:1 (the volume of coal gangue accounts for 50%), and the particle size of coal gangue is ≤8 mesh, the performance of water retention and fertilizer retention is the best, and the nutrients of coal gangue can be more comprehensively supplemented and the prepared vegetative substrate can obtain relatively best soil improvement effect, which verifies the synergy of coal gangue mixed with urban sludge to make vegetative substrate.