Study On Flue Cured Tobacco Chlorosis In Longli County, Guizhou Province

From the beginning of 2009, Leaf Chlorosis phenomenon was appeared in part of tobacco growing area of Longli country. These symptoms were similar to manganese poisoning phenomenon, also like some magnesium nutrition deficiency. Some agricultural experts couldn’t draw a conclusion. According to the survey, the disease area reached about 20 hm2 and was expanding. Baishen district of Longli country was the worst. The disease resulted in quality deterioration of tobacco and restricted the development of tobacco planting. Based on this background, this research carried out a series of experiments, such as control test of tobacco manganese poisoning and field experiments used to compare with these symptoms presenting in field. In addition, stoichiometry was employed to deduce the reasons of leaf Chorosis by comparing between normal and diseased plants. These analysis put forward some results as follow:1. Manganese poisoning provocation test show that typical characterization of single manganese poisoning of tobacco is that chlorosis presents between the veins of tobacco new leaves with yellow-white, gradually forms a small brown spot. When the concentration of Mn reached 1000mg-kg-1, these symptoms began to appear, but these symptoms were easy to vanish with reduction of Mn concentration. When the concentration of Mn was above 1500mg-kg-1, the old leaves would be infected and the symptoms couldn’t be alleviated.2. No significant correlation between the active and total Mn content in soil was found. The active and total Mg contents of soil in this region are lower than other regions. There is no significant relationship between active and total Mg contents in the soil.3.The comparison of Mn and Mg chemical metrology indicates Ca, Mg and Mn show abnormal. The ratio of K-Mg of diseased leaves is significantly greater than reference (P<0.05). The ratios of K-Mn, Ca-Mn and Fe-Mn of diseased leaves are significantly lower than reference (P<0.05). These evidences proved that there had different reasons for symptoms of Longli country.4. In annual incidence area, there is no symptom again after using dolomite powder (1500-3000kg·ha-1). For some diseased plants, magnesium sulfate solution and watered dolomite powder were sprayed on the surface or dropped among root. The diseased leaves returned green in a week by single Magnesium sulfate (three times of spraying, spraying once daily) or a combination of dolomite powder irrigation.5. The main reasons of the "chlorosis" phenomenon are as follows:the soil formed from limestone soil contained relative high manganese which was potential causes of diseased tobacco plant. The soil was acidized by chemical fertilizers, which stimulated the action of Mn and resulted in the loss of active Mg. In addition, Mg background in this region is relative low which could not satisfy the demand of tobacco.