Effects Of Atrazine On Nitrogen Fixation,Nitrification And Functional Bacteria In Black Soil

Herbicide Atrazine is widely used as a herbicide in maize cropland,and maize has a relatively wide acreage in the black soil area of northeastern China,which makes the application of Atrazine in the black soil area of Northeast China is very large,The potential threat to the ecological environment of the black soil area and the various types of biological health is particularly acute.Soil nitrogen cycling is an important part of soil geochemical cycle,which not only affects the global environmental changes,but also an important process to maintain the nutrient supply capacity and level of soil crops,and the driving action of soil nitrogen function microbes in the process Played an important role.Black soil is a kind of natural resources which is indispensable to ensure the grain yield of black soil in northeastern China.It is concerned with the critical process of nitrogen cycling in the black soil-the nitrogen fixation and nitrification,and the abundance and diversity of related microbial function genes The mechanism of response to the effect of atrazine on the nitrogen fixation and nitrification of black soil and the mechanism of revealing its related mechanism from the molecular level have important research value.Based on the above research background,this study focused on the study of the different concentrations of Atrazine stress on the nitrogen content and the transformation of black soil.On this basis,the fluorescence quantitative PCR technique was used to further study the abundance of key functional genes in nitrogen fixation and nitrification Finally,the response characteristics of atrazine to the microbial community diversity of nitrogen fixation and ammonia oxidation were explained from the microscopic point of view.The main results are summarized as follows: Atrazine significantly higher than 20 mg/kg in the initial stage(0 d),the concentration of NO3-N in the soil was significantly increased,while that of the soil treated with less than 20 mg/kg of soil(200 mg/kg)atrazine treatment in the late culture of soil nitrate nitrogen was inhibited;Atrazine on soil stress,each stress concentration of ammonium Nitrogen content decreased with the increase of culture time,and the content of mineralized nitrogen in the soil decreased with the increase of time.Under the concentration of atrazine in the soil,the concentration of mineralized nitrogen was The results showed that with the increase of atrazine stress concentration,the content of nitrogen in the soil and its transformation had a certain effect.The total nitrogen content in the soil decreased with the increase of time,The concentration of total nitrogen in soil treated with concentration(200 mg/kg)decreased significantly.The activity of urease in different soils increased with the time of Atrazine stress,and the significant difference was significant at high concentration(200 mg/kg)atrazine stress.The soil protease The activity of protease increased first and then decreased with the increase of time.Indicating that soil nitrogen converting enzyme has been affected to varying degrees.The abundance of soil nitrogen fixation gene was significantly increased at the later stage of culture(30 days),and the abundance of soil nitrogen fixation gene was promoted by fluorescence quantitative PCR.Ammonia oxidative functional gene abundance at the low concentration of atrazine(0 mg/kg,20 mg/kg treatment,with the increase of time first decreased after the increase in the high concentration of atrazine(100 mg/kg)treatment The abundance of soil ammonia oxidation gene increased first and then decreased,which indicated that the abundance of soil ammonia oxidation gene was affected in the culture process.Soil microbial biomass nitrogen increased with time,and the soil samples under each concentration of Atrazine stress increased first and then decreased,while in 0 days to 15 days,with the increase of time,each concentration of Atte The concentration of soil microbial biomass nitrogen increased gradually with the time increasing under the stress of Atrazine stress,and the significant difference was more obvious than that of other concentrations at the concentration of 200 mg/kg atrazine stress.The amount of microbial biomass carbon increased with time(0-30 d),and the soil samples under each concentration of Atrazine stress increased first and then decreased.A total of 46 major genera were detected in the soil samples of Atrazine on soil microbial biomass,and Rhizobium,Burkholderia,Bacillus,Rhizoctonia solani,Rhizobium is the dominant population.In the nif H functional gene,the number of soil OTU decreased at all and increased with the increase of the incubation time,indicating that all the soil nitrogen fixation genes were first inhibited,the species was reduced,the microbial community richness The results showed that there were three main genera in the soil samples of Atrazine and Ammonia Oxidation Microorganisms,and the bacterial communities under the stress were Nitrosospira,Nitrosovibrio,Nitrosomonas,Nitrosospira is the dominant population,followed by Nitrosovibrio.In the amo A functional gene,the number of OTU decreased with the increase of culture time,which indicated that the soil ammonia oxidized microorganism was inhibited,the species decreased,the microbial community abundance decreased,and the lower the concentration of atrazine was.From the perspective of microbial community structure,the total amount of nitrogen fixation was higher than 20 mg/kg and 200 mg/Kg at different culture time,which indicated that nitrogen fixation was affected by different concentrations of Atrazine stress.At the initial 0 days,Atrazine stress could inhibit the total amount of microorganisms in the soil samples.As the incubation time prolonged,the total amount of microorganisms in the treated soil samples increased first and then decreased on the 15 th day.On the 30 th day,the total amount of microbes in the treated soil samples decreased first and then increased,which indicated that the total amount of ammonia-oxidizing microorganisms was affected by different degrees in different Atrazine stress.Blank processing With the extension of incubation time,the number of Vibrio nitrosus flora increased first and then reached a stable quantity.From the similarity of community structure,the similarity between blank treatments was the highest at day 0,and the similarity between blank treatments was still the highest at the later stage of culture(15-30 d),indicating that they had a similarity between bacterial The results showed that the soil samples had the highest similarity between the soil samples and the soil samples treated on the 30 th day,indicating that they had little effect on the bacterial community structure.The soil samples treated with atrazine concentration of 20 mg/kg were similar to other treatments at the middle stage of culture(15 d),and the community structure of soil bacteria was significantly changed.