Effects Of Corn Herbicide Nicosulfuron-atrazine On The Emergence,Growth And Yield Of Alfalfa

The black soil region in northeastern China is one of the four remaining black soil regions in the world.Famous for its fertile soil and rich organic matter,it is suitable for cultivation.However,in recent years,the black soil region in northeastern China has faced numerous problems such as increased deterioration.Alfalfa(Medicago sativa L.),as a nutritious and high-quality forage,is being widely used in the corn-alfalfa intercropping and the management of farmland erosion ditch in the black soil region of northeastern China.It has played an important role in effectively preventing and controlling soil erosion and solving the contradiction between grain and foraging Northeast agro-pastoral ecotone.However,the alfalfa planted above is adjacent to the corn land,rare study reports that whether the herbicides sprayed in corn production have phytotoxicity to the emergence and growth of alfalfa.Therefore,in this study,alfalfa was used as the research object and a herbicide commonly used in corn land--nicosulfuron-atrazine was selected.Three different doses were set and being sprayed at preemergence,emergence stage and branching stage of alfalfa in the field.The studies aimed to research the effects of residual effects of the current year and the second year on the emergence and growth of alfalfa in the field,and the effects on seed germination in the lab.The study aimed to provide theoretical and practical guidance for the reasonable planting and application of alfalfa in the future.The results of this study are as follows:1)This corn herbicide has a significant effect on the emergence and growth of alfalfa.The spraying of corn herbicide in three different stage caused phytotoxicity to alfalfa,significantly reduced the emergence rate,inhibited the plant height and stem diameter,and reduced the dry weight per plant of alfalfa,which eventually led to hay yield was significantly lower than the control.In the first year,the branching stage treatment of alfalfa had the lowest mortality rate and had the smallest effect on plant height,stem diameter and yield,but it was still significantly lower than the control,indicating that the tolerance of this herbicide is improved with the growth of alfalfa.2)The phytotoxicity of corn herbicide to alfalfa increased with the increase of application doses,and it showed a trend of gradually increase and then decrease.Almost no phytotoxicity was observed within one week after spraying,but the phytotoxicity gradually increased subsequently,and the plant height and stem diameter decreased compared with the control.The phytotoxicity caused by the herbicide decreased over time as the spraying dose increases.The duration of the herbicide phytotoxicity to alfalfa also gradually prolonged,and the phytotoxicity of the complete dose treatment was the longest,and it still showed a trend of gradually increase then gradually decrease.3)The corn herbicide remains in the soil for a long time.This herbicides can still cause phytotoxicity to alfalfa sown after 9 months,inhibit the plant height and stem diameter of alfalfa,and significantly reduce its yield;alfalfa planted after 10 months,although no significant reduction in plant height and stem diameter,the yield was still lower than control;the alfalfa planted after 11 months is free of phytotoxicity.4)After suffering from the corn herbicide stress,the germination rate,germination energy and germination index of alfalfa treated with two third doses and complete doses were significantly lower than the control.The root-seeding ratio,vigor index,soluble sugar and soluble protein content of alfalfa treated with three doses were significantly reduced,while the content of the three types of antioxidant enzymes were significantly increased.This indicated that although the seedlings of alfalfa can improve the enzyme activity of POD,SOD and CAT to remove the reactive oxygen to cope with adversity,but the content of soluble sugar and soluble protein was significantly reduced,which resulted in the abnormal growth of alfalfa seedlings.In summary,nicosulfuron-atrazine corn herbicide has serious phytotoxicity on seed germination,seedling emergence and growth of alfalfa,and the residual effects of herbicides in the field completely disappeared when the alfalfa planted after 11 months.