Behavior And Effects Of Pyrazosulfuron And Mefenacet In "Tobacco-Paddy" System

In order to assess whether the use of the herbicide fertilizer of0.43%pyrazosulfuron and mefenacet in paddyfield can be cause to harm to the "smoke-paddy" system, this article had systematically studied the residual degradation and adsorption of this active composition pyrazosulfuron and mefenacet, and its effects on the growth and quality of tobacco. These studies were very important to assess the safety of pyrazosulfuron or mefenacet, and its related agents after it was applied in "smoke-paddy" system, and to guid its scientific and reasonable use in agricultural production.(1) By HPLC, the detemination method of pyrazosulfuron and mefenace residue in paddy water snd soil was established with added recovery experiment. Under the condition of the test, the average recoveries of pyrazosulfuron and mefenace were86.32%～94.06%and87.56%～104.07%in paddy water, its relative standard deviation(RSD) were2.08%～3.59%and2.08%～4.03%; while its average recoveries were84.00%～95.32%and84.47%～98.53%in paddy soil, with its RSD were1.39%～1.55%and0.85%～3.50%. It meaned that this method could meet the technical requirements of pesticide residue test in our country, and be applied to probe the residue snd degradation of pyrazosulfuron and mefenace after the herbicide fertilizer of0.43%was used to paddy field.(2) The degradation of pyrazosulfuron and mefenace was fit to the one-grade chemical reaction dynamics equation in paddy water, and its degradation half-life of pyrazosulfuron and mefenace were3.55d,3.10d. This showed that pyrazosulfuron and mefenace were easily degradable hercbieides (T1/2a<30d), but the degradation process of pyrazosulfuron and mefenace in paddy soil decrease gradually after a increase roughly.(3) When the herbicide fertilizer of0.43%pyrazosulfuron and mefenace was applied with180kg/ha and270kg/ha, the residue of pyrazosulfuron and mefenace in the paddy soil was very tiny and lower than its corresponding limit of detection in normal harvested paddy soil.(4) The adsorption of pyrazosulfuron and mefenace in five kinds of soil planted tobacco was fit well to the Freundlich isotherm equation; the adsorption of pyrazosulfuron was strongest in the black soil from Heilongjiang, and weakest in the cinamon soil from Shandong Qingdao; and the adsorption of mefenace was strongest in the black soil from Heilongjiang, and weakest in the tyrosinance soil from Henan Xinyang.(5) The organic matter content was the major factor which influence the adsorption of pyrazosulfuron and mefenace; in the five kinds of soil planted tobacco, the adsorption free energy of pyrazosulfuron and mefenace were less than40kJ/mol, what indicates that its adsorption in soil planted tobacco belonged to physical adsorption process.(6) When the herbicide fertilizer of0.43%pyrazosulfuron and mefenace in the soil planted tobacco, this fertilizer partly inhibited the growth of tobacco plants in the front, and the inhibition of high concentrations was more than its low concentration; there was without too much influence on growing of tobacco plants in the later.(7) After the herbicide fertilizer of0.43%pyrazosulfuron and mefenace in soil planted tobacco, it has little influence on the main chemical composition of tobacco leaves, but5times recommended dose of this fertilizer could mave the total sugar and reducing sugar of tobacco leaves content decrease, and make the protein, total nitrogen, nicotine and volatile nicotine content increase.