Influence Of Biochar On Ammonia Oxidation Microbial Community In Paddy Soil

With the ever-growing food demand, excessive fertilization caused several serious environmental issues, such as ammonia volatilization, N2O emissions and nitrogen leaching. As a kind of anthropogenic material tacking with global climate change, biochar application has the potential to manipulate the nitrogen (N) cycle in soil directly or indirectly, and thus has a profound impact on soil ecosystem function. Ammonia oxidation is the first, rate-limiting step of nitrification, and a key process in the global nitrogen cycle. Studies on the influence of biochar on ammonia oxidation microbial community in paddy soils will exert a profound foundation on increasing the nitrogen use efficiency, controlling nitrogen leaching and promoting the implementation of sustainable development of agriculture. In this thesis, five typical paddy soils in China incubated with and without the rice straw derived biochar (BC) application. The primary aim of our study was to investigate the effects of biochar on ammonia oxidation in different soils. The abundance and diversity of the ammonia oxidation bacteria and ammonia oxidation archaea community were assessed using real-time quantitative polymerase chain reaction (PCR) and Roche454sequencing technologies. The main results are summarized as follows:(1) In the greenhouse experiment, nitrogen cycle process was investigated in five typical paddy soils in China with and without BC. Results showed that biochar amendment exerts different influences on N2O emissions in different soils. The major cause for this phenomenon lies in the different influence of biochar on the ammonia oxidation of various paddy soils. The ratio of AOA over AOB varied due to the differences of soil texture. Biochar showed the potential of increasing AOB abundance and decreasing AOA abundance. Ammonia oxidation was inhibited with biochar amendment when AOA played a dominant role in the progress. However, when AOB was the major functional species, biochar amendment showed the contrary trend.(2) Roche454sequencing technologies were used to investigate the mechanism of ammonia oxidizer response to biochar. It has been found that biochar could advance the AOA diversity while decrease its abundance. The reason behind this phenomenon was that predominant AOA in paddy soil are more appropriate to inhabit in acid soil environment. The pH significantly increased with biochar additions, which led to the suppression of AOA predominant microflora. No significant effect of biochar on AOB abundance was found, while biochar showed an influence on AOB diversity to some extent which fade gradually with the passage of time.