Study On Soil Water And Salt Transportation And Numerical Simulation Of Drip Irrigation Under The Film In Cotton Field

Drip irrigation in arid and semi arid areas has been widely used in secondary saline or saline. In this study as the typical area example, throughing field experiments to explore variation of water and salt under the different irrigation quota and different irrigation cycle, analysis of soil moisture and salinity variation. On this basis, build a typical region of two-dimensional numerical simulation of salt and water movement, and using this model, compared to a variety of irrigation systems which is formulated, obtained irrigation system for the area taking water and salt of soil into account. The main conclusions of this study:(1) The results of transportation of soil water showed that irrigation amount shall not be less thanl9.35mm, according to the actual emitter discharge 3.0L/h and the layout of the situation with a dropper in study area; The difference of membrane, narrow line and wide rows decreases with the depth decreased among the three positions.All the depth of wide-line reached the maximum.The depth of water transport of narrow line has obviously been hysteresis in the 20cm, which is not obvious in the following 40cm.From the perspective of rational use of soil water to meet a single rational irrigation of cropping patterns and soil present should be between 26.1～51.3mm in the study area.(2) The results of transportation of soil water showed that the greater irrigation amount, salt accumulation, Salt transport in the soil analysis showed that the greater amount of irrigation the less salt accumulation. Salt with the wetting front and moving, wide-line performance of the most obvious; Under the existing irrigation, salinity changed little below the depth of the 60cm; Salt movement and water movement is closely related to the maximum depth of water in the wet front and basically represents the maximum width of the level of expansion of salt retention location, which can determine the vertical depth of the root 0～60cm away from the emitter to the accumulation of 0～50cm without salt conditions. Distribution of shallow salt water infiltration and transpiration is essentially the result of competition. Therefore, evapotranspiration in different periods can not only determine the water requirements of crop, but also can be identified water infiltration under different salt distribution near the crop root.(3) Established two-dimensional with root water uptake of drip irrigation model using HYDRUS-2D, and by July 2,2009～September 1 the data of water and salt in a total of 62 days to verify the model to determine the hydraulic parameters and salt diffusion parameters, established a reliable two-dimensional numerical simulation model of water and salt transport in the typical district.(4) The case of cotton, considering the crop water requirements and the local irrigation system. Through the model simulation forecast of salt and water movement during the crop growth characteristics, through the accumulation of soil salinity variation,development of appropriate irrigation system for a typical area.