| Isoxaflutole is an inhibitor of p-hydroxyphenylpyruvate dioxygenase(HPPD).It has a wide range of weed spectrum and crops,which is safe for maize,sweet potato and beet.Isoxaflutole can effectively control annual grass weeds and broadleaf weedsthrough soil treatment in maize field,especially Abutilon theophrasti Medik.?Amaranthaceae and Setaria viridis(L.)Beauv.At the same time,isoxaflutole can control weeds that are resistant to triazine and ALS-inhibitor herbicides.26% thiencabazone-methyl·isoxaflutole is composed of isoxaflutole,thiencabazone-methyl and protective agent.Because of broad control spectrum,quick effect and safety for crop,it is widely used in maize fields to control 65 gramineous weeds and broadleaf weeds.The efficacy of weed control can achieve by the triple weeding mechanism of soil application,early postemergence foliar treatment,and being activated by water.The herbicide can be used in a flexible application period.Maize can use it before 3 leaves and 1 heart,and the control time is up to 45 days.It is suitable for many tillage systems such as no tillage and less tillage,with very low dosage,and it is an ideal soil-applied herbicide for maize fields.The impact of chemical pesticides on soil microbes after application in farmland has become an indicator to evaluate safety,and it is also one of the hotspots in the research of pesticide ecotoxicology.Soil enzyme activity,as an ecotoxicological index,is used by many scholars to judge the degree of pollution of foreign substances on the soil and possible impact of foreign substances on the ecological environment.The domestic and international research on isoxaflutole and thiencabazone-methyl·isoxaflutole mainly focus on the research of variety introduction,herbicidal activity and compound preparation activity,etc.However,there is no report about its effect on the microrganisms and enzyme activities of maize rhizosphere soil.To evaluate the effect of isoxaflutole and thiencabazone-methyl·isoxaflutole on the soil microrganisms and enzyme activities in maize rhizosphere soil,in this paper,isoxaflutole and thiencabazone-methyl·isoxaflutole were taken as the research objects,and the field experiment method was used to systematically study the effect of isoxaflutole and thiencabazone-methyl·isoxaflutole on the amount of microbial biomass,microbial carbon and nitrogen,and soil urease,catalase,sucrase,neutral phosphatase,dehydrogenase activities of maize rhizosphere soil..maize The purpose of the study is to evaluate the eco-environmental safety of isoxaflutole and thiencabazone-methyl·isoxaflutole,to provide a scientific basis for the economic and rational application of the herbicides and reduce environmental pollution.The results are as follows:(1)After application with different dosages of isoxaflutole,the effect on microbial number of maize rhizosphere soil was bacteria > fungi > actinomycetes.The effect of isoxaflutole on the number of bacteria in the maize rhizosphere soil was shown to be promoted in the early stage and inhibited in the later stage.The number of bacteria treated at the recommended dose can recover to the control level in the later period of the test.The treatment of 5 times the recommended dose and 10 times the recommended dose will still inhibit the growth of the number of bacteria in the later period of the test.In addition,there is a significant difference between the 5 times the recommended dose and the 10 times the recommended dose.During the experiment,the recommended dose of isoxaflutole did not affect the number of fungi and actinomycetes in the maize rhizosphere soil.The treatment of 5 times the recommended dose and 10 times the recommended dose significantly inhibited the number of fungi and actinomycetes in the early stage of the experiment.The number can recover to the control level at 28-day after treatment,and the actinomycete can recover to the control level at 21-day after treatment.(2)The recommended dose of isoxaflutole had no significant effect on the soil microbial biomass carbon and nitrogen content compared with the control.After 7 days,5 times the recommended dose and 10 times the recommended dose of isoxaflutole inhibited the microbial biomass carbon and nitrogen content of maize rhizosphere soil,which was significantly different from the control,and could not be restored to the control level after 28 days.(3)The recommended dose of isoxaflutole has less effect on urease,catalase and sucrase in maize rhizosphere soil,and there is no significant difference from the control.The inhibitory effect of 5 times recommended dose and 10 times recommended dose is evident.The activities of catalase and sucrase can recover to the control level in the later stage of the experiment,and the urease treated with 10 times the recommended dose cannot recover to the control level in the later stage of the experiment.The soil dehydrogenase activity was inhibited during the test,and the higher the applied dose,the stronger the inhibitory effect,which was significantly different from the control and could not recover to the control level in the later period of the test.Soil neutral phosphatase activity showed early promotion and later inhibition,and the higher the applied dose,the stronger the stimulation or inhibition.After 28 days of application,each treatment did not return to the control level.(4)The number of bacteria in the rhizosphere soil of maize increased after 7 days of application,and it was positively correlated with the application dose.After 14 days,the number of soil bacteria in each dose treatment decreased,and the inhibition rate was 28.62% ? 54.09%,which was significantly different from the control.The number of soil bacteria could recover to the control level after treatment of the recommended dose and 5 times the recommended dose in the later stage of the experiment and it could not recover to the control level with the treatment of 10 times the recommended dose.The recommended dose of thiencabazone-methyl·isoxaflutole had less effect on the number of soil fungi and actinomycetes in the rhizosphere of maize,and it was significantly different from the control.After 7 days of application,the treatment of 5 times the recommended dose and 10 times the recommended dose significantly inhibited the number of soil fungi,and the number recovered to the control level after 21 days.5 times the recommended dose of thiencabazone-methyl·isoxaflutole had less effect on the number of maize rhizosphere actinomycetes,and there was no significant difference from the control.At 7-day after applying 10 times the recommended dose,it had an inhibitory effect on the number of actinomycetes,but the control level can recover after 14 days of application.(5)After treatment with the recommended dose of thiencabazone-methyl·isoxaflutole,the microbial biomass carbon and nitrogen contents in the maize rhizosphere soil were not significantly different from the control.There was no significant difference in the microbial biomass carbon and nitrogen contents between treatment with the 5 times recommended dose and 10 times recommended dose at 7-day after application.At 14-day after the application,the microbial biomass carbon in the maize rhizosphere was suppressed,which was significantly different from the control,and it could not recover to the control level at 28-day.After 21-day of application,the nitrogen content of the soil biomass decreased,which was significantly different from the control soil,and it could not recover to the control level at 28-day.(6)The recommended dose of thiencabazone-methyl·isoxaflutole had less effect on the enzyme activity of maize rhizosphere soil,and there was no significant difference from the control.The 5-fold and 10-fold recommended doses of thiencabazone-methyl·isoxaflutole has inhibitory effect on soil urease,catalase,sucrase,and dehydrogenase activities which can recover to control level later in the experiment.5 times and 10 times the recommended dose of thiencabazone-methyl·isoxaflutole had a significant inhibitory effect on the activity of neutral phosphatase and the activity cannot recover to the control level during the test. |
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