Effects Of Mesosulfuron-methyl On Rhizosphere Microbial Community And Its Combined Effect With Organic Fertilizer

Mesosulfuron-methyl acts on acetolactate synthase,which is used widely with long half-life,and may harm soil microorganisms.Organic fertilizer plays important role in improving soil fertility and soil microbial composition.The effects of mesosulfuron-methyl and its combined effect with organic fertilizer on soil properties,soil microbial composition and ecological function are not clear.In this experiment,black soil and fluvo-aquic soil were used to cultivate wheat in greenhouse.The experimental treatments were as follows:CK,pure water treatment;T1,low dose mesosulfuron-methyl treatment;T10,high dose mesosulfuron-methyl treatment;FT1,low dose mesosulfuron-methyl with organic fertilizer treatment;FT10,high dose mesosulfuron-methyl with organic fertilizer treatment.Rhizosphere and bulk soil samples were used for soil property detection and high-throughput sequencing,and finally assessed the ecological risk.The main results of the experiment were as follows:(1)Organic fertilizer could improve the soil adsorption of mesosulfuron-methyl,and the adsorption capacity increased with the increase of organic fertilizer.The experiment was carried out in the laboratory according to the batch balance method recommended by the Environmental Protection Agency.Organic fertilizers of 0%,5%,20%and 50%were added to the black and fluvial soils.The results showed that the soil adsorption of mesosulfuron-methyl could reach equilibrium within 48 hours.When 5%organic fertilizer was added,the adsorption by black soil and fluvo-aquic soil increased 11.1%and 6.8%respectively,and the soil adsorption capacity increased with the increase of organic fertilizer.The adsorption isotherm results showed that the fitting of Freundlich equation(0.8964?R2?0.9964)was higher than that linear model(0.7141?R2?0.9943).It can be seen that the use of organic fertilizer can significantly promote the adsorption of mesosulfuron-methyl in soil..(2)Available potassium,total phosphorus and available phosphorus decreased significantly after exposure to mesosulfuron-methyl,while soil organic matter,total nitrogen,nitrate nitrogen,total potassium,total phosphorus and available phosphorus increased significantly after adding organic fertilizer.Wheat was cultivated in black soil and fluvo-aquic soil in greenhouse.Wheat bulk soil was collected at seedling stage,jointing stage,flowering stage and mature stage,respectively.Soil pH,organic matter,total nitrogen,nitrate nitrogen,ammonium nitrogen,total phosphorus,available phosphorus,total potassium and available potassium were detected.The results showed that the effect of mesosulfuron-methyl on soil properties was less than that of organic fertilizer,and almost all property indexes increased significantly after the application of organic fertilizer..(3)The treatment of mesosulfuron-methyl,mesosulfuron-methyl combined with organic fertilizer had effects on the species composition,community structure and function of rhizosphere microorganisms.Total DNA were extracted from rhizosphere soil collected in greenhouse at seedling stage,jointing stage,flowering stage and mature stage of wheat.After verificated purity and concentration,high-throughput sequencing was carried out.Finally,bioinformatics technology was used to analyze the ecological effects.PCoA showed that all treatments caused significant changes in bacterial community;LEfSe analysis were used to find biomaker species.After mesosulfuron-methyl treatment,Kribbella and Streptomyces decreased significantly,Cellvibrio and Acidovorax increased significantly,Kribbell and Chujaibacte decreased,Aquabacterium and Arenimonas increased after the combined used of mesosulfuron-methyl and organic fertilizer treatment.RDA results showed that the correlation between bacterial community,organic matter and total phosphorus in black soil was strongest,and that with total potassium was lowest,while that between bacterial community in fluvo-aquic soil and amine nitrogen was significant,and that between bacterial community and total nitrogen was the weakest.The species most affected by properties were Massilia,Blastococcus and Arthrobacter The results of FPROTAX function prediction showed that the levels of plant pathogens increased after mesosulfuron-methyl trentment,after the addition of organic fertilizer,the level of chemical energy heterotrophic function increased.(4)The residue of mesosulfuron-methyl in fertilizer group was significantly lower than that in non-fertilizer group.The structural equation model was used to analyze the reasons for the low residue caused by organic fertilizer:first,organic fertilizer promoted the adsorption of mesosulfuron-methyl by soil,resulting in binding residue;secondly,organic fertilizer affected soil properties and then affected the residue of mesosulfuron-methyl;finally,the addition of organic fertilizer and the changed chemical properties led to soil bacterial community changed and promoted the degradation of mesosulfuron-methyl.The correlation analysis showed that there was a significant correlation between the residues and physicochemical factors.The relative abundance of 12 OTU significantly affected in black soil and 45 OTU in fluvo-aquic soil was significantly correlated with mesosulfuron-methyl residues,mainly negative correlation.The results of metagenomic sequencing showed that the ability of amino acid metabolism and ubiquinone synthesis in soil increased after the addition of organic fertilizer,carbohydrate active enzyme-glycoside hydrolase and glycosyltransferase were significantly affected,and the level of bacterial toxin decreased.In short,fertilization can improve the level of microbial metabolism and improve disease resistance.