The Effects Of Water-nitrogen Coupling Schemes For Flue-cured Tobacco On Its Physiological Growth And Quality Under Mulch Drip Irrigation Condition

Flue-cured tobacco is an important cash crop in China. The Vegetable and Flower Research Institute in Jiangsu Province, Nanjing Jiangning Hengxi sets three kinds of irrigation amount, 4 kinds of nitrogen application amount, 12 different water and nitrogen coupling treatments in a total, each treatment is replicated for four times. The film drip irrigation, control the flue-cured tobacco in different growth period of irrigation and fertilization of flue-cured tobacco in water and nitrogen under the action of various growth stages of the flue-cured tobacco agronomic traits, physiological traits and the dry matter accumulation and the chemical quality of flue-cured tobacco in different growth period optimal irrigation and fertilization amount. Main study conclusions are:(1)The coupling of water and nitrogen plays a significant role on the progress of each growth stage of flue-cured tobacco, apparently on the plant height. When the flue-cured tobacco lacks adequate water, the plant height is inversely proportional to the level of nitrogen application amount. In the conditions that flue-cured tobacco lacks both the amount of water and nitrogen application, it hinder increased girth of the plant. When the plant lacks the amount of wa ter while the nitrogen application is too much, it will hinder the growth of girth; while the nitrogen application is suitable, it will hinder girth stretching. However, it is obvious helpless that the high irrigation for the stretch of flue-cured tobacco leaves in the low nitrogen treatment.(2)The chlorophyll content of tobacco is hardly affected by the application of nitrogen during the process of maturation of tobacco leaves. However, the shortage of water will play a destructive effect on the protective mechanism of crop, thereby affecting the synthesis of crop chlorophyll and accelerating the formation of chlorophyll decomposition, so that the flue-cured tobacco leaves yellowing. The chlorophyll content in the growing late tobacco that have been treat ed by the water and nitrogen coupling are maintained at a high level, which indicates that the higher soil moisture content make the tobacco mature late.(3)When the irrigation is moderate, the crop net photosynthetic rate(Pn) increases first and then decreases with the change of the amount of nitrogen fertilizer. In the vigorous growing period that the irrigation amount is sufficient, Pn of the mature period of flue-cured tobacco will be in lower levels if the irrigation amount is sufficient in extension of root period or the irrigation amount reduces in mature period. In the conditions that the irrigation amount is adequate, the value of Pn is inversely proportional to the amount of nitrogen. The higher is the amount of nitrogen, the value of Pn is lower. On the contrary, the plant will need appropriate to reduce the amount of nitrogen which is conducive to enhance the value of Pn in the periods of root extending and flourishing. Under the same nitrogen application, it is not significant between the rel ationship of the vigorous leaf conductance(Gs) and the amount of irrigation. In each experimental group, the value of Ci in the mature period is greater than in the flourish period. If the tobacco is in the mature period, the amount of irrigation will have an impact in the value of Ci which increases first and then decreases. Under the same nitrogen treatment, the value of the leaf transpiration rate(Tr) with the amount of irrigation changes not apparently. With the increase amount of the nitrogen fertilizer, the value of Tr reduces.(4)In the conditions that the amount of irrigation is suitable or too much, the excessive amount of nitrogen is not only harmful to the accumulation of the dry matter in the tobacco leaves but also waste fertilizer. In the conditions that the amount of the nitrogen is same, the amount of irrigation will infect the accumulation of the dry matter in the different parts of the tobacco leaves. The amount of the accumulation of the dry matter in the leaves of the flue-cured tobacco is greater with the increase of the amount of nitrogen which indicates that they are in a proportional relationship. The different amounts of nitrogen in the different periods influence obvious to the accumulation of dry matter in the tobacco leaves.(5)The evaluation of the flue-cured tobacco comprehensive quality, the principal components, yield, irrigation water use efficiency, drip irrigation project construction is based on the national economic internal rate of return, economic net present value, ec onomic benefit cost ratio. After calculating the value of the evaluation of the entropy weight coefficient that in the condition of film drip irrigation under different water and nitrogen coupling scheme, it is determined that the W2N2 is the optimal solution, follows the W2N3 and the worst treatment is W3N1.As a result, the amount of the drip irrigation varies 9mm, 12 mm, 9mm in the roots extension, flourish and the maturity periods, and the 50kg/hm2 amount of nitrogen application could be the water and nitrogen coupling scheme of high quality and high yield of flue cured tobacco in Jiangning tobacco growing area in Nanjing.