Effects Of Ventilation Quantity On The Microbial Community And Ammonia Oxidation Activity In Cattle Manure Composting

Composting of Livestock and poultry manure was a biochemical process that the main driving force was microorganisms. Ventilation quantity is one of the most important factor in the composting process. Ammonia oxidizing bacteria(AOB), archaea ammonia oxidizing archaea(AOA), denitrifying bacteria and so on were important microbial groups involved in composting of the nitrogen cycle. Ventilation rate change could affect their diversity and richness to affect the nitrogen cycle and affect nitrogen loss in the composting.The main raw materials of compost was cow dung and lawn grass. The research was divided into two experiments. Different ventilation rate compost set three treatments for CK: 0L·min-1·kg-1 TS, treatment TF1:0.05 L·min-1·kg-1 TS and treatment TF4:0.2 L·min-1·kg-1 TS. Variable ventilation rate compost set four kinds of ventilation quantity treatments(treatment A: 0 L·min-1·kg-1 TS, treatment B: 0.2L·min-1·kg-1 TS、treatment C: 0 L·min-1·kg-1 TS at 0-14 day then 0.2 L·min-1·kg-1 TS and treatment D: 0.2 L·min-1·kg-1 TS at 0-14 day then 0 L·min-1·kg-1 TS,); The aim of research was to explore the effect of ventilation rate on microbial diversity, nirK and amoA gene and nitrogen transformation in the composting, and reveal that response mechanism of ammonia oxidizing microorganisms for oxygen concentration change.The results showed that the duration time of thermophilic phase which was over 50℃were 5 days(TF4), 9days(TF1), 0 days(CK), respectively. The highest temperature was 60℃(TF4), 63.5℃(TF1) and 42℃(CK), respectively. Ventilation treatment was useful to raise the temperature and extend duration time of thermophilic phase. Effect of ventilation rate on O2 content in the thermophilic phase was significant. Ventilation treatment could improve the nitrate nitrogen content and total nitrogen, but difference between TF4 and TF1 was no significant. The volatilization of NH3 mainly occurred in the thermophilic phase, and increased with the increase of ventilation quantity. Ventilation could improve the potential ammonia oxidation rate. Nitrogen loss was positively correlated with the ventilation rate, and the bigger the ventilation quantity, the greater the nitrogen loss. In the cow manure composting process of different ventilation quantity, the diversity of bacteria, fungi, denitrifying bacteria, AOB and AOA had significant difference. The dominant bacteria groups in the compost samples included Bacteroidetes(31.5%), Proteobacteria(25.6%), Firmicutes(13.8%), etc. In thermophilic phase, the number of Bacteroidetes from ventilation treatment compost samples was lower than CK samples significantly. In thermophilic phase, the number of Proteobacteria from CK samples was more than others, but in cooling phase and rotten phase, the influence of ventilation on the number of Proteobacteria has no obvious change trend. The dominant fungi groups in the compost samples was Ascomycota. In thermophilic phase and cooling phase, it was positive correlation significantly between ventilation quantity and the number of Ascomycota. In different ventilation quantity of composting process, the biggest correlation factor between environmental parameters and the bacterial community structure was NH4+-N content, and the next one was pile temperature. The biggest correlation factor between environmental parameters and the fungal community structure was ventilation quantity, and the next one was TOC. The dominant AOA groups in the compost samples was Crenarchaeota. It was positive correlation significantly between ventilation quantity and the number of Crenarchaeota. The dominant AOB groups in the compost samples was Nitrosomonas and Nitrosospira. In the ventilation compost samples, the number of Nitrosospira was more than Nitrosomonas. In different aeration rate of composting process, the biggest correlation factor between environmental parameters and the AOA community structure was aeration rate, and the next one was water content; The biggest correlation factor between environmental parameters and the AOB community structure was water content, and the next one was O2. Ventilation treatment could reduce the diversity and quantity of nirK gene of denitrifying bacteria to reduce the nitrogen loss from denitrification in the composting.In the variable ventilation composting, duration time of thermophilic phase which was over 50℃were 8 days(A), 9days(B), 8 days(C), and 8 days(D) respectively. B and D first entered the thermophilic phase, and the highest temperature was higher than A and C. Ventilation treatment was useful to raise the temperature and extend duration time of thermophilic phase, but after the 14 days, ventilation would only accelerate cooling. At 0-14 day, Difference of O2 content between ventilation treatment(B and D) and no ventilation treatment(A and C) was significant, and after 14 days, the ventilation rate change had significant effects on the oxygen concentration. In the thermophilic phase, the volatilization of NH3 of ventilation treatment B and D was more than A and C, in the other phase was not significant. Ventilation treatment could improve the total nitrogen content, but the difference among different ventilation treatments was not significant. Ventilation could improve the potential ammonia oxidation rate. Nitrogen loss was positively correlated with the ventilation time and the ventilation rate, and the longer the ventilation time, the greater the nitrogen loss. In the early stage of composting, the quantity of amoA gene was not significantly changed due to high temperature, but after changed ventilation quantity, the quantity of AOA amoA gene in C treated with variable ventilation increased. In 28-56 day, the quantity of AOB amoA genes: treatment of B> treatment C> treatment D, ventilation could increase the quantity of AOB amoA gene, and ventilation time was positively correlated with the quantity of AOB amoA gene. In all measured samples, the total quantity of AOA amoA genes was greater than AOB, indicating that the demand for AOA was less than AOB. Proper ventilation can improve amoA gene number in the compost. Redundancy analysis showed that the potential ammonia oxidation rate was positively correlated with the quantity of AOA amoA and AOB amoA gene, and oxygen was the most significant factor affecting the quantity of AOB amoA gene, followed by TN and nitrate nitrogen; nitrate was the most significant factor affecting the number of AOA amoA gene, followed by oxygen.To sum up, the greater the ventilation quantity was, the more nitrogen loss was. Effects of ventilation quantity on the community of ammonia oxidizing bacteria, archaea ammonia oxidizing archaea, denitrifying bacteria and so on, and the quantity of nirK and amoA gene in cattle manure composting was significant. By studying the effects of ventilation quantity on the microbial community and ammonia oxidation activity in cattle manure composting, the result could provide theoretical guidance to increase the nitrogen content of compost, reduce nitrogen loss of compost, and improve the quality of the fertilizer, etc.