Effects Of Pyrazosulfuron On The Bacterial Diversity In Paddy Soil

Pilosulfuron-methyl is one of the most commonly used herbicides in the cultivation of rice and other crops.Long-term use of herbicides can easily accumulate in soil and affect soil quality.Soil microbial community structure and diversity are important indicators of soil quality.To study the effect of pyrazosulfuron-methyl on the diversity of soil microbial communities after application of pyrazosulfuron-methyl,and to provide an important reference for evaluating soil quality changes and the effective use of herbicides.In this paper,under the conditions of indoor culture,the plate culture method was used to study the effect of pyrazosulfuron-methyl on the population of soil microorganisms;soil quality was determined by measuring the content of pyrazosulfuron-nitrogen after addition;and high-throughput sequencing technology was used.A comprehensive analysis of the changes in the community structure of soil bacteria and ammonia-oxidizing bacteria before and after application of herbicides was conducted.The main findings are as follows:The effect of pyrazosulfuron on the amount of culturable bacteria in soils of two types of paddy soil(clay,N,loam,R)was studied by plate culture method.Three treatments were set up in the experiment:no pyrazosulfuron(NCK,RCK)was added.Add 0.4 mg·kg-1 pyrazosulfuron(NL,RL)and add 4 mg kg-1 pyrazosulfuron(NH,RH).The results of the study showed that the number of soil bacteria in the two soils increased from 12h to 48h after adding pyrazosulfuron.When 0.4 mg·kg-1 of pyrisulfuron-methyl was added to the clay,the number of bacteria increased and peaked at 60 h,and the effect of high-dose pyridosulfuron(4 mg·kg-1)was not significant.The addition of low concentrations of pyrazosulfuron(0.4 mg·kg-1)in loam had no significant effect.When 4 mg·kg-1 of pyrazosulfuron was added,the number of bacteria increased and peaked at 48 h.With the passage of time,the effect of pyrazosulfuron on the amount of two soil bacteria gradually weakened and was close to the control level after the end of culture.High-throughput sequencing of the 16S rDNA gene showed that the loam contains more OTUs than the clay and the bacterial population is more abundant.The addition of pyrazosulfuron had no significant effect on the bacterial diversity of clay,but it could significantly promote the bacterial community richness and diversity in the loam,and the effect of high concentration addition was more significant.The dominance gates in different soil treatments are Proteobacteria and Acidobacteria.The relative abundances of Proteobacteria,Acidobacteria,Chloroflexi,Verrucomicrobia,and Saccharibacteria were significantly increased after the addition of low-dose pyrazosulfuron to clay.The effect of high concentration was not significant.The addition of pyrazosulfuron in loam significantly increased the relative abundance of lysates and reduced Actinobacteria.The relative abundance of Crenarchaeota.The relative abundance of Actinobacteria in loam soil increased significantly and the relative abundance of Firmicutes decreased significantly.The high concentration of pyrazosulfuron had no significant effect on Actinobacteria and Firmicutes in loam soil.There are 16 dominant genera in clay and 20 dominant genera in loam.The relative abundances are 88.34%and 87.67%respectively.The results of the significant difference test of genus genus showed that the relative abundance of loam genus significantly changed after adding azosulfuron-methyl,and there were significant differences between RH and RCK in 8 genera,and there were significant differences between RL and RCK in 11 genera;NCK and NL were only One genus was significantly different,and NCK and NH were significantly different in 3 genera.The measurement results of soil nitrogen form index showed that the change trend of nitrate content in loam soil increased first and then decreased,and clay decreased first and then increased.At the time of 12～36h of culture,the content of nitrate nitrogen in loam increased after the addition of pyrazosulfuron.The content of nitrate nitrogen increased by 57%(RL)and 53%(RH)on average in the two concentrations of pyrazosulfuron.During the 48h to 120h incubation,the addition of azosulfuron-methyl increased the nitrate content of the clay,and the nitrate nitrogen content increased by 24%(NL)and 36%(NH)on average in the two concentrations of azosulfuron-methyl.This shows that the addition of pyrazosulfuron can increase the inorganic nitrogen content in the soil and have a certain"fertilizer effect".High-throughput sequencing of the amoA gene showed that the addition of herbicides resulted in a reduction in the number of OTUs in the clay and an increase in the number of OTUs in the loam soil.The addition of high concentrations of pyrazosulfuron in the clay decreased the Chao and Ace indices significantly.The addition of pyrazosulfuron in the loam caused a significant increase in the Chao and Ace indices,indicating that the diversity of the ammonia-oxidizing bacteria added to the pyrazosulfuron-methyl clays was reduced,and the diversity of the ammonia-oxidizing bacteria in the loam soil was varied.Increased sex.The results of phylogenetic analysis showed that the dominant gate of each sample was Proteobacteria,the main dominant class was β-proteobacteria,and there were 4 known dominant genera,Nitrosospira,Thermaerobacter,Nitrosomonas and Nitrosovibrio.Nitrosospira has the highest relative abundance,and the relative abundance of Nitrosospira in clay is significantly higher than that in loam.The relative abundance of Nitrosospira in clay was increased after the addition of pyrazosulfuron-methyl at high concentration.The relative abundance of Nitrosospira in loam was decreased by low concentration and high concentration of pyrazosulfuron.