Study On The Soil Water Retention Capability And Availability Of Different Ecotype Tobacco Area In China

As an indispensability part of water resources, soil water plays a decisive role in tobacco's growth. The studies about transformation and effective using of soil water in tobacco fields have important theoretical and practical significances for the perfection of irrigation theory and technique of tobacco and the development of water saving agriculture. This paper circumfuses the water retention and supply capability of soil in tobacco fields and the effective using of soil water. The measurements for improving the behavior of soil water are also mentioned. Through the above analysis and research, the thesis comes to the following achievements and conclusions:(1) The soil water characteristic curves all fit the model of Gardner very well. Soil water characteristic curves in different tobacco fields decline rapidly in low suction condition and become smooth and slow while suction growing. The soil water retention capability in Liu-yang of Hunan province is the best, next in Luo-ning of Henan province, and the worst is in the tobacco test site of Hohai University.(2) Soil texture, organic content and ph value are the main factors influencing water retention capability of different tobacco soils and the secondary are the amount of soil capillary porosity and bulk density. In low suction condition, the soil water retention capability depends on soil texture and ph value while on organic content in higher suction condition.(3) Sandy soil has more available water and less unavailable water than clayey soil. The water supply capacity of Liu-yang and Luo-ning is better than Jiang-ning and En-shi. The conclusion under the correlation analysis of specific water capacity and soil physical-chemical properties is that specific water capacity has significant relativity to soil specific gravity and capillary porosity as the same as to soil bulk density when suction between 0.02×10~5Pa and 10×10~5Pa, and is positively correlated with organic content and ph value and clay, but is negatively with total porosity.(4) Available soil water is connected closely to soil texture, organic content, bulk density and capillary porosity. So sand, clay and organic content are chosen to be variables in the total available soil water regression analysis. A simple and feasible...