Studies On Mechanism Of Humic Acid To Improve Quality And Yield Of Flue-cured Tobacco

Experiments which had humic acid of several qualities as basic fertilizer of flue-cured tobacco in pot and field was carried out to study the effect mechanism of humic acid in promoting the development Quality and Yield of flue-cured tobacco. The result of two-year experiments indicted that:1. Humic acid had an obvious influence in promoting physiological activity of flue-cured tobacco. Humic acid Could improve photosynthetic capacity of tobacco, which causes photosynthetic rate and pigment content improvement, promotes the activity of some enzyme such as nitrate reductase, catelase ascorbic acid oxidase, and polyphenol oxidase in the body of flue-cured tobacco. Thus, humic acid made the physiological metabolism more active, raised the development and the ability of resisting adversity raised in tobacco body. As a result, the disease situation of tobacco mosaic and black shank was effectively controlled.2. Humic acid could reduce pH value of soil, increase the content of organic matter as well as available N,P,K and promote the activity of saccharase and phosphatase in soil related to soil fertility As a result, humic acid could improve the nutrient conditions in soil, increase the capacity of soil for supplying nutrients, and create a good soil microenvironment in which roots of tobacco could grow and absorb nutrients well.3.Humic acid absorbed by tobacco had an positive effect on enhancingrespiration of root due to improvement of the activity of a series of important respiratory enzymes such as ascorbic acid oxidase and polyphenol oxidase thus casuing the root developing well, raising the dry weight volume and length of root. At the same time humic acid promoted the activity of root which stimulated the root absorbing capacity for more nutrients and increased the ability of compounding in root. As a result tobacco could grow well and form higher quality and yield of leaf eventually.4. Having inspected the economic index and analyzed the inter chemical compounds of cured tobacco, we can draw the conclusion that humic acid could promote the ratio of superior and middle class,unit leave weight,output value and yield of cured leaves. The contents of K, Nicotine and flavor precursor were also improved under the action of humic acid. Furthermore the important chemical elements were well-matched and balanced and all quality index were more reasonable in cured leaves by the treatment of humic acid. In the end, the flue-cured tobacco quality were improved.5. Compared the comprehensive results of three humic acid treatments applied in flue-cured tobacco, soil we could conclude that the B treatment was the best. This indicated that the effect made by humic acid was not positive correlation with the quantity of humic acid applied. There was a suitable range which humic acid could have best effect upon tobacco development, quality and yield .The good effect would reduce, and even show a negative effect if applied more quantity of humic acid in tobacco planting .