Effects On The Growth Of Flue-cured Tobacco Under Different Negative Pressure Water Supplying And Potassium Fertilizer Models

Adopting the homemade negative pressure irrigation device to supply water for tobacco, this paper studies the dynamic change of soil moisture in different negative pressure water supply, and effects on the growth, physiological characteristics, yield and quality of flue-cured tobacco, water and fertilizer utilization rate under different water supplying and utilization rate of fertilizer under different negative pressure and potassium application mode in this paper. The main results are summarized as follows:1. In the range of-10--20kPa, the soil moisture would be in the range of 13.35%-21.46%, and it didn't appear the phenomenon of drought and flood cycle. During the growing process, there was no obvious proportional relationship between the soil moisture content and the pressure2. Compared with conventional irrigation, it could effectively promote the growth of flue-cured tobacco by negative pressure irrigation in-10?20 kPa, and the effect of promting is obvious with the increasing of water pressure. It's favorable to the tobacco by applying the model of integrating water and fertilizer at fast-growing and mature stage, but the conventional methods of potassium fertilizing is better for growth of tobacco at root stretch stage.3. At rosette stage, the root activity could be increased with reducing the pressure, and the suitable pressure for nitrate reductase and the content of photosynthetic pigments is about-20kPa and -15kPa respectively. At fast-growing stage, the suitable pressure for nitrate reductase activity is about -15kPa, while the root activity and Photosynthesis reduce as water pressure reduced. And when the pressure is below-15kPa, water-supplying becomes one of the main factors which limiting the net photosynthetic rate. At mature stage, the nitrate reductase activity reaches the maximum when the pressure is about -15kPa, and the content of photosynthetic pigments was positively correlated with the pressure, but root activity is small affected by the pressure in this stage4. In the range of -10?20 kPa, reducing the pressure of water supply is beneficial for the formation of root system, and dry weight of root was less affected by the models of potassium fertilizer during the root-extended period. When the pressure was-20 kPa, it increased by 76.6% compared with conventional irrigation in this stage. At fast-growing and mature stage, it could moderately improve the accumulation of all dry matter and the ratio of leaves dry matter, which had positive effect for the tobacco leaf output, if the water and fertilizer management mode of integrating water and fertilizer in the-10?15 kPa was used in the tobacco field.5. In the range of -10?20 kPa, properly increasing the pressure could obviously improve the content of potassium and carbohydrate of tobacco leaves. When the pressure was in-10 kPa, the content of K increased by 11.9%?30.9% compared with other treatments. In addition, using the mode of integrating water and fertilizer also has positive effect for increasing the content of K.6. In the range of -10?20 kPa, according to the pressure decreasing, water consumption would decrease significantly, while WUE and potash utilization rate would increase. To some extent, adopting the conventional methods of potassium fertilizing could reduce water consumption with reducing the amount of potassium fertilizer, but WUE, the amount of nitrogen, phosphorus and potassium absorption could also be reduced at the same time. WUE of T4 and T5 was respectively increased by 15.2% and 9.9% compared with conventional potassium application. The amount of nitrogen and phosphorus absorption show first increasing and then decreasing with the pressure, and which nitrogen and phosphorus absorption of-15 kPa treatment, compared with the traditional irrigation treatment, were respectively increased by 23.3% and 41.7%. Using the model of integrating water and fertilizer, it could obviously improve the utilization rate of potassium.Comprehensive analysis from the growth, yield, quality, efficient utilization of irrigation and utilization rate of fertilizer, a model of integrating water and fertilizer in the negative pressure irrigation should be proposed. On this basis, the water parameters for the growth of tobacco was quantified, the suitable pressure of water supply for flue-cured tobacco at various growth stages as follows:-15?20 kPa at root stretch stage,about -10 kPa at fast growing stage, and-10?15 kPa at mature stage.