Effects Of Atrazine On Bacterial Community Structure In Cultivated Black Soil Layer Of Cold Region

Atrazine is a common herbicide in maize field.Although it can effectively control farmland weeds and increase crop yield,its long-term application leads to persistent pollution of agricultural ecological environment,especially on soil ecosystem.Soil microbes are the sensitivity indexes that reflect the health status of soil ecosystems.The effects of pesticides on the diversity of soil microbial community structure in different tillage soils are systematically studied from the perspectives of tradition,biochemistry and molecular factors.To evaluate the safety of soil ecosystems and pesticides Application has important theoretical guidance.In this study,the soil in the maize continuous cropping area in black soil of cold region was studied as the research object.The influence of atrazine on soil bacterial community structure in different cultivated soil layers was clarified.Based on the detailed analysis of the temporal and spatial change rule of atrazine in different cultivated soil layers in different periods of black soil of cold region,the changes of soil enzyme activity,microbial community structure,function and diversity were analyzed.To provide a scientific basis for guaranteeing the sustainable application of black soil.The main results are as follows:1)The changes of atrazine in different cultivated soils and different periods in black soil of cold region were clarified.The results showed that in black soil in cold area atrazine residual level changes over time within a year is gradually reduced,and from the vertical distribution of soil,the residue will gradually leach into the deep soil,and there is a cumulative process in the deep soil.When the residue accumulated to the maximum,then gradually reduced.The residual amount of atrazine in 10～20cm and 20～30cm soil layer gradually accumulated from the application and reached the maximum at 15 days after the application,and then the residue gradually decreased.The digestion rate of atrazine in the0～10cm and 20～30cm soil layers was above 93% and the half-lives were 24.75 d and 33 d,respectively.The digestion rate of the soil was only 76.86%,in 10～20cm soil layer,Half-life up to 63 d.2)The effects of atrazine on soil enzyme activities were studied at different stages in different soil layers.The results showed that atrazine had different effects on soil enzyme activities in different tillage soils at different times.Atrazine had a certain increase effect on the activities of urease and polyphenol oxidase in different cultivated soils at different stages after application,while sucrase and phosphatase activities were not affected by atrazine in different tillage soils at different times Impact.3)The effects of atrazine on the physiological functions of microbial community carbon metabolism level in different cultivated soils and different periods in black soil of cold region were investigated by Biolog technique.The results showed that atrazine inhibited the diversity and overall activity of microbes in 0-10 cm and 20-30 cm soil layers,while,the total activity of soil microorganisms in 10-20 cm soil layer was not inhibited,and its diversity was inhibited.The results showed that in the 0 to 10 cm soil layer,for 7 d,15 d,31 d and 130 d after applying pesticide atrazine,Shannon diversity index,Simpson index,Mc Intosh index and overall microbial activity(AWCD value)of soil microbes show basically the change trend of suppression-weakened suppression-gradual recovery-increase;and the change trend is increase-suppression-weakened suppression-increase in the 20-30 cm soil layer.However,the changes of Shannon,Simpson and Mc Intosh diversity indices of soil microbes at 7,15,31,and 130 days after application of atrazine in the 10-20 cm soil layer were basically expressed as suppression-enhanced suppression-suppression-increase.The overall activity(AWCD)is expressed as suppression-stimulation-increase-increase.In other words,atrazine inhibits the diversity and overall activity of microbes in 0-10 cm and20-30 cm soil layers,but the overall activity of soil microorganisms in 10-20 cm soil layer was not inhibited,and the diversity was inhibited.In addition,based on the metabolic analysis results of microbes on six carbon sources in Biolog ECO plate,the relative utilization of microbes on six carbon sources in the Biolog ECO plate is not affected by the atrazine in different tillage soil layers at different times in black soil of cold region.However,from the point of the whole experiment,the utilization degree of microorganisms on six carbon sources from high to low is followed by saccharides > carboxylic acids >amino acids > polymers > amines > phenols.4)The effects of atrazine on soil bacterial community composition and diversity were studied by 16 S r RNA sequencing.The results showed that the composition of the bacterial community at each classification level was basically the same in the three different tillage soils of 0-10 cm,10-20 cm and 20-30 cm in black soil of cold region.The atrazine did not change the community structure of the bacteria,but the relative abundance of each group is slightly changed.Atrazine had a certain inhibitory effect on the diversity of bacterial communities in different cultivated soils in black soil of cold region,but with the decrease of atrazine residue,the inhibitory effect was decreased.The results showed that atrazine contaminated soil bacterial community composition mainly covers 12 phyla,26 classes,35 orders,39 families,34 genera,22 species.Based on the distribution of bacterial community composition in three soil layers,the results showed that Proteobacteria,Acidobacteria,Actinobacteria and Gemmatimonadetes were the dominant bacteria in the three soil layers.The total relative abundance of the sample accounts for 79.3%.Atrazine had a certain inhibitory effect on acidobacteria and Gemmatimonadetes in three different tillage soils at different times in black soil of cold region.According to the results of five Alpha diversity indices of Ace,Chao1,observed number of species,PD-whole tree and Shannon,the above five Alpha diversity indices show that the diversity of microorganisms in 0-10 cm soil layer of atrazine contaminated soil has the same trend,which respectively shows the trend of suppression-weakened suppression-gradual recovery-increase at 7d,15 d,31d and 130 d after applying pesticide.In the 10-20 cm soil layer,there was a trend of suppression-enhanced suppression-suppression-increase.The variation trend in the 20-30 cm soil layer can be summarized as increase-suppression-weakened suppression-increase.