Impact Of Different Crops And Fertilization On Ammonia Oxidizing Bacteria And Archaea In Black Soil

Soil microorganisms are an important part of soil, and they are the main power insoil nutrients transformation, soil organic matter resolving and the forming of humus.Besides, crops, fertilization and the interaction of crop-fertilization may influence thesoil microbial communities and the function in farm ecosystem. In this study, wetaking16S rRNA gene as molecular target and adopted the next generation454pyrosequencing to investigate the effect of farm management on the microbialabuncance and community. At the same time we adopted the454pyrosequencing andDNA-stable isotope probing technology （DNA-SIP） investigate the contribution ofammonia oxidizing bacteria and archaea under long-term fertilization. The mainconclusions were drowm as follows:Based on Hailun Agricultural Ecology Station of Chinese Academy of Sciences,the microorganism （bacteria, fungi and actinomyces） and abundance ofammonia-oxidizing bacteria （AOB） and ammonia-oxidizing archaea （AOA） affectedby different crops （such as soybean, maize and wheat） were investigated. The resultsshowed that among the three different kinds of crops, the amount of bacteria wasmuch larger than that of fungus and actinomycetes in soils. The soil microorganismamount was significantly affected by different crops roots（P<0.05）and was in thefollowing order: soybean>wheat>maize. The abundance of AOB and AOA was notsignificantly influenced by different crops. The fertilization of nitrogen significantlyincreased the abundance of AOB in maize and wheat, and has no significant effect onsoybean, while the nitrogen fertilization decreased the abundance of AOA. Thephosphorus fertilization did not change the abundance of AOB and AOA abundance.A pot experiment was carried out in greenhouse to study the effect of fertilization and root system of wheat on the soil microbial amount, the abundance of AOB andAOA, urease and phosphatase activity. The microbial amount, urease activity andphosphatase activity of treatment CK were significantly increased by39.0%,302%and38.5%by wheat. The microbial amount, urease activity and phosphatase activitywere significantly increased by24.6%⁴7.0%,17.2%³2.7%and21.2%²5.9%withfertilizer application but without wheat planting. Fertilization treatments with wheatplanting increased the soil microbial amount, urease activity and phosphatase activityby3.3%³1.4%,59.0%¹68%and15.2%²6.7%, respectively. With wheat planting,the abundance of AOB was significantly decreased by44.1%, while the AOAabundance was increased by29.5%. N fertilization significantly increased the AOBabundance by264%³13%, while P fertilization only increased by the AOAabundance by4.94%. Fertilization significantly decreased the AOA abundance by23.8%⁴8.5%. Fertilization treatments with wheat planting significantly decreased theabundance of AOB and increased the abundance of AOA.Based on21-year fertilization experiment, we found that after21-yearfertilization the microorganisms which proportion>4.39%in no fertilization soilwere suppressed, while the microorganisms which proportion <4.39%were promoted.And the long-term fertilization decreased the microorganism diversity, the Ninfluenced the microbial community diversity much more than the P fertilization.Further more, the functional importance of AOB and AOA was studied asaffected by21-year fertilization.¹⁵N-isotope tracing demonstrated that ammoniaoxidation activity was significantly stimulated under near-in situ condition infertilized NPK soils when compared to the control soil of CK treatment that receivedno fertilization. Pyrosequencing results clearly showed that AOB abundance wassignificantly increased while the AOA was not by the21-year fertilization.Furthermore,¹³CO₂-based DNA stable isotope probing （SIP） suggested thefunctional importance of bacterial ammonia oxidation in both CK and NPK soils. However, strong proliferation of archaeal ammonia oxidizers was demonstrated incontrol but not fertilized soil.Therefore, N fertilization significantly increased the AOB abundance anddecreased the AOA abundance, and decreased the microbial diversity. And long-termfertilization of urea leads to the functional extinction of AOA.