Effects Of Fomesafen And Clethodim On Soil Microbial Community Diversity

Fomesafen and clethodim are widely used to control broadleaf and grassy weeds respectively in soybean fields.While long-term application will result in herbicide accumulation and quality decline of soil.Soil microbial diversity is an important indicator of soil quality,and the distribution and growth status of microorganisms in soil are the result of the interaction between soil environment and microorganisms.Therefore,to study the effects of fomesafen and clethodim on the diversity of soil microbial community are of great significance in revealing the quality change,pollution monitoring and remediation of soil.In this study,the soil physical and chemical properties and soil enzyme activities were measured after treatment with different concentration of herbicides.The effects of fomesafen and clethodim on soil microbial functional diversity were studied with Biolog ECO plate culture method;Illumina high-throughput sequencing technology was used to analyze the changes of soil microbial community structure before and after herbicide treatment.The main results are as follows:1.Effects of fomesafen and clethodim on soil physical and chemical properties and soil enzyme activity.The recommended dose,10 and 500 times recommended dose of fomesafen,clethodim and the mixture of two were used to treat black soil without any herbicide Incorporation.45 days later soil physical and chemical properties were determined.The pH value of soil descended with the ascending of the application concentration.The contents of AN,TN and OM increased after treatment in all treated samples.The content of AP and AK increased in fomesafen-treated samples.While the content of AP decreased with the addition of clethodim and the mixture of two herbicides and the content of AK was not significantly different from that of the control group.Urease and dehydrogenase activity of the herbicide-treated soil were measured at 7 days,15 days,30 days and 45 days respectively.The results showed that fomesafen treatment could increas soil dehydrogenase activity,whereas the addition of clethodim and mixed herbicides inhibited dehydrogenase activity.2.Effects of fomesafen and clethodim on soil microbial functional diversity.The microbial functional diversity of the herbicide-treated and control samples was measured at 7 days,15 days,30 days and 45 days.With the increase of fomesafen concentration,the microbial metabolic activity was enhanced.The Shannon index and Simpson index of X1 and X10 group changed inconspicuously,while the indexes of X500 treatment was significantly reduced.The McIntosh index of X10 group was higher than that of the control group,and the McIntosh index of other treatments were significantly lower than that of the control.The microbial metabolic activity was negatively correlated with the concentration of herbicide after mixed herbicide treatment;the Shannon index and Simpson index decreased;the McIntosh index of FX10 group was lower than that of the control group,and the McIntosh index of FX500 was significantly decreased.3.Analysis of soil microbial community structure by Illumina High-throughput Sequencing.Illumina high-throughput sequencing results showed that the fomesafen and clethodim had obvious effect on soil microbial community structure.Before and after herbicide application,the dominant species of microorganisms were unchanged,but the proportions were different.The dominant bacteria mainly spread in phylum Proteobacteria,Actinobacteria and Acidobacteria.The proportions of the dominant bacteria all increased after herbicide treatment.The dominant fungus was mainly distributed in phylum Ascomycota.The proportion of the dominant fungus decreased after fomesafen treatment and increased in other samples.The results showed that the microbial community structure of fomesafen-treated soil was the most similar to the control.Abundance and diversity of soil microorganisms presented significant difference after treatment by clethodim and the mixture of two herbicides.