Deposition Of Acetochlor In Maize Ecosystem And Its Relationship With Pharmacodynamics

As an inevitable product of the progress of science and technology and the development of human civilization,pesticides have made irreplaceable contributions to the development of national economy,the safety of agricultural production,the health of the people and the harmony and stability of society.Among those,acetochlor is a one of amide herbicides which is commonly used in the northeast jade fields.It is often used in maize,soybean,rape and other dry fields to control annual grasses and some broad-leaved weeds before budding.With the large-scale use of acetochlor,many negative effects also appear.Due to the degradation products of them may harm non-target organisms,improper use will have adverse effects on soil environmental quality and subsequent sensitive crops.Therefore,the succession of harmful biological community was single,the resistant weeds increased,the amount of pesticide increased,the residual pollution and drug damage were serious,which seriously affected the ecological environment.In this study,the deposition and digestion of acetochlor in the target area of maize planting system were studied,the relationship between pesticide deposition and efficacy was discussed,and the minimum effective dose for pest control was determined.The relationship among pesticide application rate,target deposition amount and control effect was clarified.At the same time,the degradation rule of acetochlor in different conditions was studied under controllable indoor conditions,and the main influencing factors of acetochlor degradation were preliminarily determined.Furthermore,the effects of different concentrations of acetochlor on microbe in black soil of farmland were studied in order to provide accurate data of eco-environmental effects and guarantee for scientific and rational application of acetochlor.The results were summarized as follows:(1)The relationship between the deposition amount and efficacy of acetochlor in maize planting system was studied.According to the registered concentration of acetochlor,soil and plant samples were taken to measure the deposition and digestion rule of soil and plant in different period of maize planting,different dosage of field application,soil treatment before seeding,soil sample and plant sample,respectively.At the same time,the effect of acetochlor on weed control was investigated 40 days after the application of acetochlor..The results showed that the effective concentration of acetochlor was 675,1012.5,1350,2025 g/hm~2,and the original deposition in Jilin was 0.633~1.824 mg/kg and 1.928~4.307 mg/kg,respectively.The original deposition in the plant was 0.191~0.316 mg/kg and 0.187~0.478 mg/kg.With the increase of application time,the amount of acetochlor deposition in soil decreased gradually.The half-life of acetochlor in soil was 6.8~11.7 days and 8.3~9.9 days in two years respectively,and the digestion rate of 40 days was more than 90%.The half-life of acetochlor in the plant was 3.8~5.1 d and 5.4~6.0 d,and the degradation rate of acetochlor was more than 90%at the 30th day.Acetochlor residue was not detected at all concentrations during the harvest period.When the concentration of acetochlor in soil was more than 1350 g/hm~2 for 40 days,the total control effect of acetochlor in soil was over 90%when the concentration of acetochlor was 0.017~0.154 and0.158~0.202 mg/kg,respectively,to the main control weeds such as Cordyceps japonicus,barnyardgrass and Cordyceps davidiana at the concentration of more than 1350 g/hm~2.(2)Through the study on the degradation factors of acetochlor in maize field soil,the sustainability of acetochlor degradation in soil ecological environment was further evaluated,and the effect of different environmental factors on the degradation rate of acetochlor was clarified.Three typical farmland soils(black calcium soil,meadow black soil and white soil)in maize field of Jilin Province were used to study the effects of acetochlor on different soil types and water contents under controllable indoor conditions.The degradation law of acetochlor under different temperature and other herbicide addition conditions was studied,and the external factors affecting the degradation of acetochlor were preliminarily investigated.The results showed that the degradation rate of acetochlor raised with the increase of organic matter content under the same treatment.The effect of temperature on the degradation of acetochlor was the most obvious.When the temperature increased from 5 to 35?,the half-life of the soil decreased from 44.6 to 13.2 d,respectively.The degradation speed of acetochlor in soil was also related to the soil moisture content.With the increase of soil moisture content,the degradation rate accelerated.When the soil moisture content increased from 5%to 20%,the half-life was shortened from 25.6 to 14.7 d,respectively.There was no significant effect on the degradation rate of acetochlor by adding different concentrations of herbicide interaction,which indicated that the degradation rate of acetochlor in soil was positively correlated with temperature and water content.(3)The effect of acetochlor on soil microorganism in black soil was discussed.The microbiological effect of acetochlor in black soil environment was clarified,and the effect of acetochlor on microbial activity in black soil environment was revealed.The microbe quantity in black soil of corn field was investigated by treating corn field soil with different concentration of acetochlor.The results showed that every concentration of acetochlor could inhibit the bacteria in soil for 7 days,and only the highest dose(2025 g/hm~2)could inhibit the bacteria at30 days.After 45 days,the inhibition was relieved and gradually tended to the control level.7days after application,the inhibition increased with the increase of the concentration of fungi,and the number of fungi returned to the normal level after 30 days.Actinomycetes showed strong adaptability to acetochlor.7 days after application,the promoting effect was enhanced with the increase of dosage,and then gradually returned to the normal level.At the same time,the trend of acetochlor on soil enzymes were studied,and there was no significant effect on catalase in each treatment concentration,but the inhibition effect on soil urease in high concentration and low concentration was not obvious.The effect of soil dehydrogenase on soil dehydrogenase raised with the increase of application concentration.