The Influence Of Hexazinone On Sugarcane And Its Interplanted Crops

Hexazinone is a sym-triazine herbicide with systematic selectivity and post-emergence contact poison, which was developed by DuPont in 1974. Recent researches indicated that the application of hexazinone on the weed control in sugarcane fields generates great prospects. However, no studies have been found that is related to the influence of hexazinone on sugarcane and its interplanted crops. This paper studied the residue dynamics of hexazinone on sugarcane plant and soil, the effects of hexazinone on the growth and physiology of sugarcane and its interplanting, and the relationship between residue doses and the degree of phytotoxicity. This study provides a scientific basis for environmental safety evaluation of hexazinone on weed control in sugarcane field. The results are shown as follows:1. Developed a method for determination of hexazinone residues in sugarcane, peanuts, maize, soybean and soil. The samples were firstly extracted with acetonitrile containing 1%(v/v) acetic acid, and then were added Sodium Citrate and MgSO4 to construct a buffer system. Secondly, the soil samples were analyzed by using UPLC-UV, while the plant samples were cleaned-up by mixing adsorbents of PSA and MgSO4 and detected by GC-ECD. As a result, the average recoveries were between 80.44% and 102.81% with RSD less than 5.55%. The method satisfied the demands of residue analysis of pesticide.2. Studied the residual degradation dynamics of 25% hexazinone SL in sugarcane plants and soil. The result suggested that the residual degradation dynamics of hexazinone in plants and soil was in accordance with the first order dynamics. The half-lives of hexazinone were respectively 19.8 d in plants and 7.69 d in soil.3. Studied the influence of hexazinone on the indexes of chlorophyll content, photosynthetic rate, activity of antioxidant enzymes and MDA. The study demonstrated that low concentration(≤ 120 g a.i/hm2) of hexazinone could result in the increase of chlorophyll content, photosynthetic rate and activity of antioxidant enzymes(SOD、POD、CAT) while decreasing the content of MDA. With the dosage of hexazinone increasing, the chlorophyll content, photosynthetic rate and activity of antioxidant enzymes in sugarcane leaves decreased significantly, while the content of MDA went up.4. Studied the effects of hexazinone on the growth of sugarcane. Pot experiments and field experiments were conducted to observe the influence of hexazinone on the appearance indicators including plant height, leaf length and fresh weight. In addition, the sensitivity difference of several sugarcane varieties against hexazinone was tested. The result showed that the hexazinone less than 120 g a.i/hm2 displayed a promoting effect on sugarcane growth. If the amount was larger than the safe dose, the growth of sugarcane wound be inhibited and phytotoxicity symptoms wound appeared. The sensitivity of sugarcane to hexazinone was related to strain and variety. The varieties of GT series for resistance to the herbicide hexiazinone was stronger than ROC and YT. When 25% hexazinone SL was applied at the dosage of 58.608 per 0.0667 hectar (hexazinone content in double recommended dose of 60% hexazinone+diuron WP), it was safe to the growth of sugarcane.5. Conducted pot experiments to evaluate the sensitivity of hexazinone on peanuts, maize and soybean. A quantitative model y= a+bln(x) was established to study the relationship between residual quantity and phytotoxicity degree in the soil and plants. The comparison of EC10 and EC50 indicated that soybean presented the highest sensitivity to hexazinone, while peanut exhibited strongest resistance According to the pesticide hazard, hexazinone was determined to be high risk for these three plants. The correlation coefficients of chlorophyll relative inhibition rate and concentration of hexazinone were higher than 0.9, which was at the highest imitation degree. Thus chlorophyll was more sensitive than plant height and fresh weight.