Influence Of Herbicides Applied At Previous And Temporal Stubble On The Growth Of Tobacco

The survey were carried out with questionnaire about the herbicides applied at previous and temporal stubble in Hunan main region of tobacco, of which the investigation is main on the kinds of herbicides in paddy field. Aiming at soil samples and phytotoxicity of tobacco plants, samlping and detection are taken in main tobacco planting areas of the whole province. Via researching and detecting, we have found that there’re some kinds of herbicides used in preceding bed of tobacco seedling and causing tobacco herbicide injury, such as Quinclorac, Acetochlor, Butachlor, Paclobutrazol, ect. Quinclorac has the most severe phytotoxicity in tobacco, and it has the longest residence time, which more than one year. By sampling in tobacco planting regions of Quinclorac, we’ve done its degradation curve, and worked out that the Quinclorac’s half-life is43.12d, which degraded more slowly.Maybe, as a result of adding into inadaptaing pesticides of soil microorganisms, Quinclorac has an effect on the activity of soil polyphenol oxidase, which shows up as a trend of Inhibition-activation-inhibition. While on the third day, Quinclorac had a galvanising impact on the activity of polyphenol oxidase, and ti’s maybe resulted from Microbial stress response or additive carbon source (or energy). On the7th day, it turned into inhibition, it maybe associated with the accumulation and toxicity of degradation products. Overall, the enzymatic activities in soil is significantly higher in about three days. The peroxidase(POD) and Polyphenol oxidase in leaf are significantly higher in about22d.And the chlorophyll is significantly higher in about5d.Tobacco herbicides phytotoxicity has several types, mainly including Leaf rolled, Leaf thick green, Plants dwarf, Heartleaf distortion, ect. In the production, we found that Quinclorac is used most in paddy fields, and the phytotoxicity of tobacco plant is more serious. For example, when it used Quinclorac over1.5times than its recommended dose, the tobacco appeared leaf rolled, turned smaller and distorted, even only had the vein after happened the phytotoxicity, thus resulted in losing economical worth. There are some phytotoxicities to tobacco when using Glyphosate in near by the bed of tobacco seedling, and the main symptoms of phytotoxicities are smaller leaf and serrated leaf margin. If the Paclobutrazol misused, it will resulted in tobacco curly, shrinking into a round shape, but don’t stunt.By taking tests in three spots, the safeners being able to release the hazard of herbicide of tobaccos and performancing better mainly include Plant source antidote1and Plant source antidote2. Other drugs include Magnesium Oxide, Trace element Vitacat added0.01%Brassinolide, ect, but the effect in three tests is inconsistent, mainly due to the herbicides have different degrees effect on tobaccos. Besides, the time to spray is different, therefore there are different effects. We found in practice that spraying earlier, the effect to ease the herbicide phytotoxicity better; and the herbicide phytotoxicity less serious, the effect to ease better.Screening of microbial degradants has to be studied further. Microbial degradation bacteria can be isolated and screened from the bed of tobacco seedling in main tobacco planting areas, or the soil and water near by factories produced Quinclorac.