Effects Of 1,3-D Fumigation On Bacterial Community And Nitrogen Transformation In Continuous Cropping Soil

Due to the restricted use of methyl bromide in agriculture,1,3-dichloropropene(1,3-D)has become a potential substitute.Previous studies have found that 1,3-D can effectively control pests and diseases in soil and increase crop yield,but little is known about the effects of 1,3-D fumigation on soil bacterial community and nitrogen cycle.Therefore,the laboratorysimulation test and the field trials were used to evaluate the effects of 1,3-D on soil nitrogen,soil properties,soil enzymes,nitrogen cycle-related coding genes and bacterial diversity after 1,3-D fumigation.QPCR and high-throughput sequencing were combined to investigate the effects of 1,3-D fumigation on bacterial abundance and diversity,as well as 16 S functional prediction to analyze the biological mechanism of 1,3-D affecting nitrogen transformation.The main research results provided a theoretical basis to the environmental safety assessment,and offered technical support for obtaining its registration in China.The main results were as follows:(1)Laboratory experiments and field experiments demonstrated that 1,3-D inhibited activities of urease and protease in a short period of time,and then the enzyme activities gradually recovered,indicated that 1,3-D had no long-term effects on the enzyme reaction involved in the nitrogencycle.The recovery rate of soil urease and protease in the field was faster than that under laboratory conditions.(2)In this study,we observed an increase in ammonium nitrogen and a decrease in nitrate nitrogen content,indicated that soil nitrification was inhibited.In the early stage of the experiment,there was a significant dose effect between the ammonium nitrogen content in the soil and the 1,3-D concentration.As the dose of 1,3-D increased,the ammonium nitrogen content increased with the extension of the sampling time.The content of ammonium nitrogen in the fumigation soil gradually decreased,and there was no significant difference between the control and the control group.Nitrate nitrogen had the opposite trend.(3)Under different 1,3-D doses,soil microbes had different degrees of inhibition,and the use of 1,3-D could significantly reduce the number of culturable microorganisms in the soil.q PCR analysis of total bacteria,ammonia-oxidizing archaea and ammonia-oxidizing bacteria revealed that the use of 1,3-D also inhibited the number of these microorganisms,and the number of these microorganisms gradually recovered in subsequent sampling.(4)In the early stage of the experiment,the use of 1,3-D could reduce the microbial diversity in the soil,change the relative abundance of the species and the microbial community structure,including microbial diversity and community structure.Forthermore,microbial diversity and community structure are closely related to sampling time and 13-D dose.(5)The abundance of nitrogen-related enzymes in the soil changed with the dose of 1,3-D and the sampling time.In 0,4,16 WAT sampling,the use of 1,3-D reduced the abundance of nitrogen-related enzymes in the soil,while in 1,8,12 WAT sampling,the use of 1,3-D increased the abundance of nitrogen-related enzymes.The rate of increase in denitrification-related enzyme abundance was higher than that of ammonia monooxygenase abundance,which might explain the decrease in nitrate nitrogen content.