Reasearch On Screening Of Nitrogen Preserving Agent And Mechanism Of Nitrogen Preserving In The Process Of Composting Cow Manure

Nitrogen loss is serious and common in livestock manure composting process.How to effectively reduce nitrogen loss during composting has become the key to improving composting.Adding various kinds of exogenous substances as nitrogen preserving agents in the high-temperature aerobic composting process can effectively reduce nitrogen loss,improve fertilizer efficiency,and mitigate potential risks to environment during the composting process.However,the existing nitrogen preserving agents on the market have certain limitations on the nitrogen retaining effect of high-temperature aerobic compost.Whether a new type of nitrogen preserving agent can be found to effectively suppress nitrogen loss and reduce the pollution caused by the pile body to the environment during high-temperature aerobic composting needs further discussion.In addition,searching more nitrogen preserving agent formulas and studying its effect and mechanism of composting nitrogen retention can better promote the development of composting of livestock and poultry manure in China.In this paper,fresh cow dung was used as the research object,and the high-temperature aerobic compost was used to study the nitrogen retention effect and mechanism of different nitrogen preserving agents,and the best nitrogen preserving agents were selected.The research includes the following aspects:(1)Through indoor simulation experiments,the effects of different proportions of ferrous sulfate,calcium sulfate and their mixing with biochar on the nitrogen loss during the high-temperature aerobic composting of cow dung straw straw were selected,and the nitrogen preserving agent formula was initially screened;(2)Based on the simulation test,a composting test was conducted to verify the nitrogen retention effect of adding ferrous sulfate and biochar as a nitrogen preserving agent during the composting process of cow dung,so as to select the nitrogen preserving agent formulation with the best nitrogen retention effect;(3)Through high-throughput sequencing,the microbial community structure was analyzed,and the relationship between the nitrogen retention effect of biochar and ferrous sulfate as a nitrogen preserving agent and functional flora was explored.The main findings are listed as below:(1)In the simulation test,compared with the treatment of the control group,treatment 3and treatment 5 had better nitrogen retention effects,with total nitrogen loss rates of 25.43± 1.05% and 16.89 ± 0.79%,respectively.And the other physical and chemical indicators meet the requirements of the national standard for harmless feces(GB7959-87).(2)In the field experiment,adding ferrous sulfate biochar mixtures in different proportions as nitrogen retention agents can shorten the composting time(3 to 5 days)and promote the compost maturation.Compared with all treatments,treatment 5 has the best nitrogen retention effect.The Kjeldahl and ammonium nitrogen contents are the highest at the end of composting,respectively 23.5g / kg and 0.86 g / kg,the nitrate nitrogen content was increased by 146.6% compared with the control group,and the reduction rate of total nitrogen loss was 59.23 ± 2.04%.(3)During the megathermal and maturation period of cattle manure straw composting,the predominant flora at the phylum level for the treatment 5 with the best nitrogen retention was Proteobacteria,Actinobacteria,Bacteroidetes,Firmicutes;Azotobacter were most active in the megathermal period,and Proteobacteria which containing azotobacte was account for37.62%.The predominant flora at the genus level in the megathermal phase is Chelativorans,Pseudoxanthomonas,Chelatococcus,Streptomonospora,Bordetella and Flavobacterium.The dominant flora in maturation phase was Parapedobacter,Pseudomonas,Streptomyces,Rhizobium,Rhizobium,Bacillus.Among them: Rhizobium can coexist with legumes to intercept nitrogen to achieve nitrogen retention effect,accounting for 16.77% in the megathermal period;Chelatococcus is resistant to high temperature and can be denitrified to fix nitrogen,accounting for 5.57% in the megathermal period.