Effects Of Long-term Nitrogen Application On Soil Culturable Bacterial Diversity And Nitrogen Transformation Function

Soil microorganisms are a key component of the underground ecosystem and play an important role in maintaining terrestrial ecosystems and soil biogeochemical functions.Studying the response mode of cultivable microorganisms to soil nitrogen and their function in nitrogen transformation will help to understand the role of microorganisms in soil nitrogen transformation.This study is based on the long-term positioning fertilization test station of Shenyang Agricultural University,using the extreme dilution plate method,combined with16 S r RNA and PCR molecular detection technology,analysis of different fertilization treatments(no fertilization control,CK and application of inorganic nitrogen fertilizer,N4),the soil can be cultivated The abundance,population diversity and nitrogen transformation potential of bacteria,discuss the effect of long-term application of inorganic nitrogen fertilizer on soil microbial abundance and species diversity,and preliminarily analyze the nitrogen transformation potential of soil microorganisms.The research results show that long-term application of inorganic nitrogen fertilizer can significantly increase the content of ammonium nitrogen and nitrate nitrogen in the soil,while significantly reducing the soil p H value.In the experiment,85 strains of cultivable bacteria were isolated,of which 59 strains were treated with CK and 26 strains were treated with N4.The test results of the abundance of cultivable bacteria in the soil showed that compared with the treatment without fertilization,long-term application of inorganic nitrogen fertilizer not only significantly reduced the number of cultivable bacteria in the soil(CK,59;N4,26),but also the species of bacteria that can be cultivated Diversity is also significantly reduced(CK,22;N4,14).The 16 S r RNA identification results of cultivable bacteria showed that in the soil without fertilization(CK),the isolated cultivable bacteria were in the taxa at the phylum level,and the number of strains was: Proteobacteria> Actinomycetes> Firmicutes,And in the soil of long-term fertilization treatment(N4),the number of cultivable bacteria is: Actinomycetes> Proteobacteria>Firmicutes.On the taxa at the genus level,22 genera were isolated from soil without fertilization(CK)and 14 genera were isolated from N4 soil.The research results of cultivable bacteria's nitrogen conversion potential(ammonification,nitrification,denitrification andnitrogen fixation)showed that the ratios of cultivable bacteria with ammoniation,nitrification,denitrification and nitrogen fixation capacity in the treatment without fertilizer(CK)were respectively 64.6%,7.5%,62.5% and 72.3%.Long-term application of inorganic nitrogen fertilizer(N4)to the soil,the proportion of cultivable bacteria in the soil with the ability of ammonification,nitrification,denitrification and nitrogen fixation is 31.6%,0%,64.7%,and63.2%,respectively.Nitrogen transformation functional gene detection showed that strain CK-F-41 has the potential of ammonification,nitrification and denitrification;strain CK-F-59 has the potential of ammonification and denitrification.