Preparation And Application Of Biochar-based Microbial Fertilizers

Biochar,as a functional material,possess developed pore structure,huge specific surface area,abundant functional groups,surface charges and strong adsorption properties,etc,which can effectively adsorb and hold moisture and nutrients.Studies have shown that biochar as a carrier material mixed with NPK fertilizers can not only improve the utilization rate of fertilizers but also have good effects on the improvement of soil properties and crop yield.Biochar provides a new direction for the resource utilization of agricultural waste and the production of highly efficient and environment-friendly fertilizers.On the other hand,microorganisms are nutrient activator which are also important in agricultural production.Although the research and development of microbial fertilizers has been developing rapidly,there is a lot of resistance in promotion of application of it,because it is not easy to transport and save.Biochar can provide a good habitat for microorganisms as a carrier material.The addition of microorganisms on the biochar-based fertilizers might make fertilizer be more fully functional and better application effects.However,little study was conducted on microbial compounding with biochar and chemical fertilizers.Therefore,the research on the production of biochar-based microbial fertilizers will give an important guiding significance for the development of fertilizer industry,and also provide scientific reference and new ideas for the development of efficient agriculture and sustainable agriculture.In this thesis,rice husk biochar,pecan shell biochar and bamboo biochar prepared from three kinds of typical agricultural wastes were selected.The biochar materials with the better adsorption performance were selected through the analysis of the properties and the adsorption experiments of NPK.Then,the rice husk biochar,NPK fertilizer,and microbial spores were prepared for the development of biochar-based microbial fertilizers,using three different technologies including the mixed method,adsorption method and mixed granulation method.The properties of these biochar-based microbial fertilizers including the pH value,the total nutrient content,the number of living bacteria,and nutrient release characteristics were determined.Finally,the effects of the biochar-based microbial fertilizers were explored through pot experiment by analyzing the properties of the soil and the Chinese cabbage.The main results are as follows:(1)The physical and chemical properties of rice husk biochar,pecan shell biochar and bamboo biochar are all suitable for fertilizer production.All three kinds of biochar are alkaline,high carbon content,high specific surface area,rich pore structure and active functional groups.According to the results of properties among the three kinds of biochar production,it is presumed that rice husk biochar had better adsorption capacity than bamboo biochar and pecan shell biochar.(2)The results of adsorption experiment showed that all three kinds of biochar had certain adsorption effects on NPK,and that the adsorption capacity of biochar was affected by the pH,reaction time,initial concentration and biochar addition.Moreover,the equilibrium adsorption quantities were the largest under the conditions of pH 9,adsorption time 3 h and initial concentration 100 mg · L-1.With the increase of the amount of biochar,the equilibrium adsorption quantities of NPK increased but unit adsorption quantities decreased.Three kinds of biochar had better adsorption effect on nitrogen and phosphorus than potassium.In terms of adsorption properties,rice husk biochar was best,followed by bamboo biochar,pecan shell biochar was poor.(3)The biochar-based microbial fertilizers prepared by mixed method,adsorption method and mixed granulation methods.The preparation technology,the amount of rice husk biochar and the types of microorganisms have impacts on the properties of the biochar-based microbial fertilizers.The biochar-based microbial fertilizers prepared in this paper were rich in carbon and nitrogen and other organic elements,the pH values were acidic or near neutral,the total nutrient content was up to standard of the national fertilizer.Also,some differences were shown of the properties of biochar-based microbial fertilizers.The mixed granulation biochar-based microbial fertilizers loaded the most material,followed by adsorption method and the mixed method.Three kinds of microorganisms in granulation of fertilizers can still maintain strong activity after 60 days,in which the effective viable count of bacillus mucilaginosus krassilnikov is obviously higher compared with bacillus megaterium and bacillus subtilis.Biochar-based microbial fertilizers can slow release of nutrients,and impacted mainly by the preparation technology and the amount of rice husk biochar.Totally,the biochar-based microbial fertilizers had the best slow-release effect which prepared by mixed granulation method and the amount of rice husk biochar 30 percent.(4)The results of pot experiment showed that compared with conventional fertilization and no fertilization treatments,the treatment of biochar-based microbial fertilizers improved the properties of soil and Chinese cabbage.The pH value of soil was closer to neutral.The organic matter content,total nitrogen,available phosphorus,available potassium and other nutrient content were greatly increased by biochar-based microbial fertilizers application.The biochar-based microbial fertilizers treatment significantly increased the maximum leaf length,maximum leaf width,plant height,fresh weight and the content of NPK,reduced the nitrate content of Chinese cabbage.(5)The preparation technology and the amount of biochar addition have a great impact on the biochar-based microbial fertilizers,compared with the microbial species.Our results showed that,the biochar-based microbial fertilizers with rice husk biochar content of 30 percent by mixed granulation method have optimal application effects on soil nutrient improving and Chinese cabbage growth.