Effects Of Biochar Addition On Soil Fertility Reclamation From Coal Mining Subsidence Area

The reclamation of coal mining collapse area lead to severely damaged soil structure, extremely low soil organic matter content and fertility levels, which seriously hampered agricultural production. It is an urgent matter to be handled to improve the soil fertility, increasing farmland resources to sustainable development.Biochar is a product of pyrolysis,whereby organic materials of either plant or animal origin are heated in a low or no oxygen environment and has been demonstrated to be a potentially beneficial soil amendment in agricultural. We adopt laboratory aerobic incubation under constant temperature and humidity control, intermittent leaching and pot experiment to study the effect of biochar on soil nitrification, organic nitrogen mineralization, physicochemical properties, the microbial activity, and the growth of crops. In this experiment, the effect of biochar addition on soil nitrification and on mineralization characteristics of organic nitrogen provided by chicken manure and sheep manure under different nitrogen levels was studied by adopting laboratory aerobic incubation method under constant temperature and humidity, and a vegetable soil was used as control. The pot experimental treatments included the combination of biochar in different ammounts with nitrogen fertilizer or chicken manure.setting the treatments with no C、N addition, or the combination of wheat straw with nitrogen fertilizer as controls. The main results were showed as follow:1. It turned out that soil nitrification rate was relatively low in soil from reclamated coal mining subsidence area and slower than the vegetable soil.Biochar can inhabit nitrification in a given period, especially when applied with high level of nitrogen fertilizer. Soil nitrification rate was also relatively low in soil from vegetable soil when applied with high level of nitrogen fertiliger.2. The results showed that the organic nitrogen mineralization was higher in reclamated soil with chicken maure compare with sheep manure treatment. Biochar could inhibit chicken manure mineralization obviously, and this phenomenon was more significant than in vegetable soil.lt found that the cumulative amount of total nitrogen leaching of vegetable soil with chicken maure less than the control0.3%,8.02%.The total nitrogen leaching of the treaments of reclamated soil with chicken maure were less than CK21.63%,28.34%, while it was no difference between the sheep manure combinated with amount of Bc and non-added Bc.3. Biochar can reduce the bulk density and improve the cation exchange capacity of the soil from reclaimated subsidence area as well as promote the reservation capacity of nutrient elements.Biochar could increase the soil total nitrigen content. The available phosphate concentration was higher in the soil treated concurrently with organic fertilizer, but biochar had little effect on the content of total phosphate and alkali-hydrolyzable nitrogen, wheras the content of alkali-hydrolyzable nitrogen raised slightly in the late wheat growth stage. The combination of nitrogen fertilizer with biochar increased ammonium nitrogen concentration in the soil. Biochar had showed a significant role in promoting ammonium nitrogen content in soil, with no influence on nitrate nitrogen at maturation stage of wheat when applicated with organic fertilizer.Soil available K concentration increased with the increment of biochar when applied with nitrogen fertilizer, but had no response to amounts of biochar when applied with organic fertilizer.The combination of nitrogen fertilizer of biochar addition with0.5%,1%,2%,4%were higher11.02%,25.60%,36.88%,90.83%than0%,respectively.Microbial biomass carbon and nitrogen increased significantly with biochar application.The combination of biochar with0.5%,1%were increased43.67%,63.16%respectively to only combinated with nitrogen fertilizer.However,high amount of biochar inhibited soil C/N ratio to a certain extent, and decreased microbial nitrogen content in the later growth stage compared with the previous stage.The principal component analysis revealed that as the application rate of biochar increased, the main component score indicating the utilization capacity of carbon sources by microbe increased in soils treated concurrently with manure fertilization. However,the score of due to the interaction between the two main components, indicating an inhibited soil microbial activity in the treatments of biochar application with nitrogen fertilizer.Compared with vegetable soil, the utilization capacity was higher for carbon sources as sugars, amino acids, and lower for carboxylic acids in soils from reclamated mining subsidence area. However, addition of organic fertilizer, wheat straw or biochar decreased the utilization capacity of carbohydrate by microbes.Gemination was inhibited by addition of biochar, and this inhibition was more obvious with increasing charcoal application rate. However, this phenomenon did not last for long. Biochar application had no effects on wheat biomass accumulation, but increased wheat yield. However, biomass accumulation and yield production of plants fertilized with organic manure showed no response to biochar addition, and there was no significant difference compared with the CK treatment.