| Trifloxysulfuron sodium is an ultra-efficient sulfonylurea herbicide combining low toxicity and high selectivity, which is widely applied to control Cyperu srotundus in sugar cane fields. Currently, there is few literature reports about the residues of trifloxysulfuron sodium in soil of sugar cane fields, and the safety studies about its impacts on interplanted crops. This paper studied the digestion law of trifloxysulfuron sodium residues in soil of sugar cane fields and its influencing factors, developed the injury diagnosis of its impact on several interplanted crops in sugar cane fields such as peanuts, watermelons and corns, and conducted research on the relationship between residue doses and the degree of phytotoxicity. Then, we evaluated the safety of trifloxysulfuron sodium application on crops. The results provided a scientific basis for the safe use of trifloxysulfuron sodium in sugar cane fields, and the technical support for the round interplanted crop patterns of sugar cane fields. The results were summarized as follows:1. A method for determination the residue of trifloxysulfuron sodium in peanuts, watermelons and soil was developed. The samples were extracted with acetonitrile, acidized with0.085%phosphoric acid solution, extracted with acetonitrile, then concentrated the supernatant. The residues of trifloxysulfuron sodium were detected by HPLC-UV. The result indicated the limit of detection of trifloxysulfuron sodium was0.1×10-9g, limit of quantification of trifloxysulfuron sodium was0.005mg/kg. Average recoveries of trifloxysulfuron sodium in peanuts samples were at the range of89.1to102.8%at three spiking levels from0.05mg/kg to1mg/kg with relative standard deviations of2.11to3.15%. Recoveries and RSD of the method at spiked concentrations between0.05mg/kg to1mg/kg were89.9to97.7%,1.72to2.51%for watermelons samples, and88.9%-107.7%,2.08%-5.10%for soil samples. These results showed that the sensitivity and precision of methods accords with demands of residue analysis of pesticide.2. Some comparative experiments were designed to assess the safety of two nutgrass herbicides to sugarcane under dosage of application with cover spraying. The results showed that when the75%trifloxysulfuron sodium water dispersible granules was applied at the dosage of22.5g a.i./hm2in the4-5leaves stage of sugarcane, it caused only a little injury even non-injure to sugarcane, while a considerable injury could be seen at0.45g a.i./hm2and0.45g a.i./hm2to240g/L imazapic agent.75%trifloxysulfuron sodium WDG could provide higher safety to the crop.3. Combined with laboratory tests, field trials investigated trifloxysulfuron sodium safety of interplanting crops.(1) Laboratory tests establish y=a+blnx model, which shows a good quantitative relationship between residual quantity and phytotoxicity degree in the soil and crop body. The dose-response model correlation coefficients is above0.86, this experiment found that sensitivity about trifloxysulfuron sodium caused on different types of crops is different, the order of three kinds of the crop for trifloxysulfuron sodium sensitivity is corn> peanut> watermelon. Different parts of the same crop on trifloxysulfuron sodium sensitivity are also differences. In the concentration range of0.05～1mg/kg, the order of sensitivity in peanuts and corn to trifloxysulfuron sodium is root length> root weight> height> plant weight, while the order in watermelon is height> plant weight> root length> root weight. The correlation coefficient of residues-reaction model is above0.99, which is higher than the dose-response model. Residues-reaction model reveals the reason that the plants absorb trifloxysulfuron sodium is the cause of inhibition differences in various parts of the plant.(2) Field trials was conducted to evaluate the effects of trifloxysulfuron sodium on peanuts, corn and watermelon. Trifloxysulfuron sodium has play a role in promoting growth to corn plant height, watermelon vine longer, when seeding peanuts interval90d after agent spraying at recommended dose, the inhibition rate of plant height, leaf number, number of pods per plant, yield and other indicators in harvest period is less than5%, it is safe to peanuts. For watermelon, the inhibition of watermelon vine is10.5%, while watermelon advances into the reproductive period when setting watermelon interval30d after agent spraying. The growth of watermelon vine is25.1%when setting interval90d compared with the control. The yield is less than3.5%after the interval90d setting corn, it is also safe for corn. According to the field of peanut injury diagnosis, investigation and data statistical analysis, established quantitative classification standard for crop phytotoxicity.4. An incubation experiment was conducted to study the dynamic response of soil respiration in two kinds of sugarcane field soil for the first time. The results showed that different concentrations of trifloxysulfuron sodium promote lateritic red soil respiration, while low concentration (1mg/kg) trifloxysulfuron sodium restrains red soil respiration, high concentration (100mg/kg) promotes red soil respiration. After30d, there existed no significant difference in the amount of emission CO2between the treatment and the control in two kinds of soil.According to hazard coefficient rules, trifloxysulfuron sodium belongs to no actual harm pesticide levels. It is therefore concluded that the herbicide trifloxysulfuron sodium in normal use may not cause persistent and significant effect on respiration of the soil.5. Trifloxysulfuron sodium in soil degradation in line with the first-order kinetics. In a certain range, the higher the temperature, the more beneficial to the degradation of trifloxysulfuron sodium degradation. It is the same to the humidity of soil. Compared with the humidity, temperature significantly affects the degradation of the agent.6. Trifloxysulfuron sodium leaching characteristics in two different physical and chemical properties of soils, which was studied by soil column leaching method. The results showed that:trifloxysulfuron sodium is more difficult to move in lateritic red soil, R2+R3+R4>50, belongs to "more difficult to be leached". Trifloxysulfuron sodium difficult to move in red soil, R1>50, belongs to "difficult to be leached". |
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