| Corn is the main grain crop in China.According to the latest statistics,in 2017,the planting area of corn in China had reached 35.454 million hectares,while the area of corn field damage in the same year has reached 20 million hectares.while the area of grass damage in corn fields has reached 20 million hectares in the same year.TThis made the loss of corn production extremely serious.Therefore,the chemical control of weeds is the top priority in ensuring corn production.The use of herbicides has played a positive role in ensuring corn production,improving corn quality and improving production efficiency.However,in recent years,the amount of herbicides used in corn fields has been increasing,and the control effect has not been as good as before,and it has caused a series of problems such as serious damage to corn fields and shortened cycle of resistant weeds.In particular,some corn field soil treatment herbicides are susceptible to environmental factors and become more likely to migrate in the soil,resulting in unstable efficacy,hazard planting and environmental pollution.Increasing the dosage of the herbicides will exacerbate these problems.In addition,in recent years,there are few new herbicide varieties in corn field,and the herbicide mixture mode is single.Therefore,how to reduce the herbicide dosage while ensuring the herbicidal effect has become a concern of corn chemical weeding researchers.The herbicide adjuvant has a short development cycle and low cost,and plays an important role in improving the efficacy of herbicides,reducing the amount of herbicides,and improving the safety of crops on crops,it can effectively solve the problems of efficacy and pollution in the application of herbicides in corn fields.In this paper,the synergistic effect of new adjuvant on corn field herbicides was studied systematically by instrumental analysis and biological activity test methods.And the effects of new adjuvant on the soil behavior of corn field soil treatment herbicide thifensulfuron-methyl under different environmental conditions and the effects of new adjuvant on the physical properties of the corn field foliage treatment herbicide atrazine in corn field were studied,thus clarifying the synergistic mechanism of new adjuvant in corn field herbicide.At the same time,the synergistic effect of new adjuvant on corn field herbicide mixture and its effect on corn safety were studied.The main research results are as follows:(1)The new adjuvant could significantly improve the herbicidal activity of the corn field soil treatment herbicide acetochlor and thifensulfuron-methyl.The higher the concentration of new adjuvant,the more obvious the synergistic effect.(2)The increase of soil p H or soil organic matter content could reduce the volatilization ofthifensulfuron-methyl in the soil;The increase of soil temperature or soil water content could increase the volatilization of thifensulfuron-methyl in the soil.The new adjuvant could reduce the volatilization of thifensulfuron-methyl in soil under the conditions of different soil temperature,different soil p H,different soil organic matter content and different soil water content,respectively;Under the same environmental conditions(the same soil temperature or the same soil p H value or the same soil organic matter content or the same soil water content),with the increase of the amount of new adjuvant,the volatilization of thifensulfuron-methyl became lower and lower.(3)The increase of soil temperature,soil p H value or soil water content could reduce the adsorption of thifensulfuron-methyl on the soil,and the increase in the soil organic matter content led to an increase in the amount of adsorption.The new adjuvant could reduce the adsorption of soil on thifensulfuron-methyl under the conditions of different soil temperature,different soil p H values,different soil organic matter content and different soil water content,respectively;Under the same soil environmental conditions(the same soil temperature or the same soil p H value or the same soil organic matter content or the same soil water content),with the increase of the amount of new adjuvant,the adsorption amount became lower and lower.(4)At the same soil depth,the concentration of thifensulfuron-methyl distributed at each point was significantly different.The addition of new adjuvant could affect the lateral distribution of thifensulfuron-methyl in the soil,and with the increase of the concentration of new adjuvant,the standard deviation of the four-point concentration in the same soil layer was smaller,the fitting degree is better,and the distribution was more uniform.(5)The increase of soil p H,soil water content or rainfall could deepen the leaching depth of thifensulfuron-methyl in the soil and the thifensulfuron-methyl concentration of soil samples at the same distance;when the soil organic matter content increased,it showed a completely opposite trend.The new adjuvant could reduce the leaching depth of thifensulfuron-methyl and the thifensulfuron-methyl concentration of soil samples at the same distance under the conditions of different soil temperature,different soil p H values,different soil organic matter content and different soil water content,respectively.Under the same environmental conditions(the same soil p H value or the same soil organic matter content or the same soil moisture content or the same soil rainfall),the higher the amount of the new adjuvant added,the shallter the leaching depth of the thifensulfuron-methyl,and the lower the detected concentration of the thifensulfuron-methyl in soil samples at the same distance.(6)The new adjuvant could effectively improve the herbicidal activity of corn field herbicides,atrazine,mesotrione and nicosulfuron,and the higher the amount of new adjuvant the more obvious the synergistic effect.(7)Atrazine 900 ga.i.·hm-2 mixed with new adjuvant could decrease the surface tension and drying time,and increase the spreading diameteris and viscosity.And the higher the concentration of the new adjuvant,the more obvious the synergistic effect.The amount of new adjuvant(V/V)added was 0.1%,0.3%,and 0.5%,respectively,compared with the control,the surface tension ofthe atrazine liquid was reduced by 32.60%,37.50% and 43.60%,respectively;The viscosity increased by 23.24%,32.16%,and 37.80%,respectively;The spreading diameteris increased by22.44%,32.95%,and 43.61%,respectively.The drying time was reduced by 15.90%,31.52% and38.58%,respectively.(8)The new adjuvant could significantly improve the herbicidal activity of corn field soil treatment herbicide mixture(acetochlor + thiophenesulfuron)and foliage treatment herbicide mixture(nicarsulfuron + mesotrione + atrazine).The higher the amount of the agent added,the more obvious the synergistic effect.The higher the amount of new adjuvant added,the more synergistic effect on herbicides.The addition amount(V/V)of new adjuvant was 0.1%,0.3%,and0.5%,respectively.The fresh weight control effect of soil treated herbicide mixture on grass weeds increased by 10.93%,14.85%,and 17.55%,respectively.The fresh weight control effect of broadleaf weeds increased by 11.91% and 13.80%,respectively.The fresh weight control effect of stem and leaf foliage treated herbicide mixture on grass weeds increased by 9.13%,12.16% and17.29%,respectively.The fresh weight control effect on broadleaf weeds increased by 8.81%,12.89% and 15.78%,respectively.(9)The use of new adjuvants alone or in combination with cornfield herbicide mixture would not inhibit the growth of corn and development and had no effect on corn yield. |
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