The Mechanism Of Organic Nitrogen Transformation During Vegetable Wastecomposting

Since the implementation of the “vegetable basket project” by the state,China's vegetable industry has developed rapidly.With the increasing of vegetable acreage,vegetable production,and residents' demand for vegetable quality,it also breeds a major environmental safety issue that a sharp increase in vegetable waste needs to be managed.These large quatities of vegetable waste contain large amounts of nutrients(e.g.nitrogen,phosphorus and potassium).It should be returned to the farmland system using aerobic compost.However,the nitrogen cycle of aerobic composting is usually accompanied by nitrogen loss.Therefore,in order to achieve the purpose of comtrolling nitrogen loss,it is of great significance to explore the contribution of different organic nitrogen components to ammonium nitrogen formation during composting.In this experiment,vegetale waste compost with two bulk agent(wheat straw and corn stalk),and four amendments(biochar,calcium superphosphate and two microbial additives).To explore the conversion of organic nitrogen fractions,and the contribution of organic nitrogen fractions transformation to ammonium formation during different composting.Meanwhile,it discusses the microbial mechanism that functional microorganisms in nitrogen transformation during vegetable composting.The main results are as follows:(1)Ammonium contents decreased 79.6% and 51.4% during vegetable waste composting with wheat straw and corn stalk,respectively.Compared to vegetable waste compost without amendments,ammonium contents increased 30.07% and 5.64% during vegetable waste composting using biochar and calcium superphosphate,the loss rate of ammonium contents decreased 3.12% and 17.07% during vegetable waste composting using two microbial additivies as amendments.(2)Based on combination path analysis with the total effect of conversion of organic nitrogen components on the ammonium formation,we found that: Of all the tupes of nitrogen present in vegetable waste compost,ammonium was mainly formed from amine nitrogen during vegetable waste composting with wheat straw,while ammonium amino acid was mainly formed from nitrogen during vegetable waste with corn stalk.Amino sugar nitrogen was synthesized from ammonium during vegetable waste composting with wheat straw and corn stalk,respectively.Ammonium was mainly formed from amino acid nitrogen and amino sugar nitrogen during vegetable waste composting using biochar as amendment,ammonium was mainly formed from amino sugar nitrogen and amine nitrogen during vegetable waste composting using calcium superphosphate as amendment,ammonium was mainly formed from amino acid nitrogen and hydrolysable unknown nitrogen during vegetable waste composting using second microbial addictive as amendment.Hydrolysable unknown nitrogen was synthesized from ammonium during vegetable waste composting using biochar and calcium superphosphate as amendments,respectively.Amino acid nitrogen and amino sugar nitrogen were synthesized from ammonium during vegetable waste composting using second microbial addictive as amendment.Four organic nitrogen fractions were synthesized from ammonium during vegetable waste composting using first microbial addictive as amendment.(3)Nitrite reductase,urease,asparaginase and protease promoted the formation of ammonium.Ammonium transformed into stable nitrogen compounds under the action of nitrate reductase.Nitrate reductase,nitrite reductase and urease played leading roles in nitrogen transformation.Total organic organic and electronic conductivity promoted the mineralization of organic nitrogen into ammonium.The temperature and pH decreased the amount of nitrogen transformed into ammonium by inhibiting the activity of nitrite reductase.The total organic carbon was the primary factors driving the changes in enzyme activities.In vegetable waste composting using biochar calcuim superphosphate as amendments,humin acid,fulvic acid and pH promoted the formation of ammonium.Microbial biomass nitrogen,dissovled organic carbon,total organic carbon and moisture content decreased the amount of nitrogen transformed into ammonium.Fulvic acid and microbial biomass nitrogen played leading roles in nitrogen transformation.In vegetable waste composting using two microbial addictive as amendments,moisture content promoted the formation of ammonium.A lot of ammonium were promoted to form humin acid and fulvic acid by microbial addictive.Electronical conductivity and fulvic acid played leading roles in nitrogen transformation.(4)A total of 19 phylums,54 classes,109 orders,249 families,and 611 genera were detected during vegetable composting.Weissella,Lactobacillus,Cyanobacteria-unidentified,Leuconostoc,Escherichia-shigella,Acinetobacter were the host bacteria of aprA.Weissella,Lactobacillus,Cyanobacteria-unidentified,Leuconostoc,Escherichia-shigella,Acinetobacterwere the host bacteria of chiA.Firmicutes-uncultured-1,Lysinibacillus,Aeribacillus,Firmicutes-uncultured-2,Ureibacillus,Corynebacterium were the host bacteria of amoA.Firmicutes-uncultured-1,Corynebacterium,Peptoclostridium were the host bacteria of HAO.Through the correlation analysis of functional microbial community structure changes and physicochemical properties,it was found that the humification process can reduce the loss of ammonium by protein degradation,and the humification process also promoted ammonia oxidation.