Influence Of Water Movement In Soil Under Micro-Irrigation By Using Numerical Simulation

Drip irrigation as an efficient water-saving irrigation technology is widely used in arid or semi-arid regions such as Xinjiang, we using buried pipes to reduce the impact on soil water and salt transport by evaporation as usual, namely subsurface drip irrigation(SDI). Moistube-irrigation is a new water-saving technologies, by means of continuous irrigation through underground micro-moistening pipe, taking the moisture to the plant root zone for crop water requirements. Numerical simulation is simple, fast, and flexible, when given an initial and boundary conditions can be used to simulate various factors and their combinations on the areas of soil water flow, solute transport, heat transfer and plant root water uptake. Most researchers is often just to prove that the simulated and measured values closer. Using the proven analog data reasonably approximate the true value and validated data for multi-factor Simulation test is still insufficient. Knowing the law of capillary arrangement and moist soil water movement under SDI and moistube-irrigation is very important for drip irrigation and moistube-irrigation design in science and make the control of the movement of soil salinity the reasonable. By underground application HYDRUS- 2D software, under different irrigation methods to simulate water movement, focusing on the technical elements of subsurface drip irrigation time, dripper flow, irrigation interval, etc. The conclusions of this four effects on the water flow law under SDI and moistube-irrigation is following:1. with the increase of irrigation time, the time of migration of moist peaks at vertically upward reached the surface trends fit power function, while at the vertical downward and horizontal this transport distance obeys a power function trends increasing; in different directions the wetting front migration distance increasing trends as power function with dripper flow increased and growing trends logarithmically with the increase of irrigation frequency.2. with the addition of dripper flow the coefficients and index of power function of wetting front migration distance varies with increasing irrigation time in three directions showed trends parabola, wherein the index in vertical turns parabola and opening up, other coefficients and exponents parabola are opening up in other direction; and near the peak in the dripper flow 1.5L / h place.3. Wetted area were linear with the growth of dripper flow and irrigation time increases;with the increase of the irrigation interval decreases exponentially, which the curve slope of dripper flow under wet humid area is greater than irrigation time. Wetted area and dripper flow and irrigation time increases in direct proportion to the increase and the irrigation interval is inversely proportional.4. With the distance between two emitters increasing the time of wetting front migration distance reach to surface and moist area after the intersection to form a "saddle" disappearance of the time were increased; near the drip, different irrigation time, dripper flow, irrigation interval and emitter spacing combinations on soil water movement more significant, within 40 cm of drip influence of these four factors in soil water movement is not obvious.5. Compared the law of water movement under SDI and moistube-irrigation through numerical simulation found that near underground dropper(the distance is less than 5cm)both moisture and soil water potentials distributed symmetric neither under SDI or moistube-irrigation. Then at influence of gravity and intermittent the moisture and soil water potential changes fast at down of vertical than other directions under SDI, and the moisture and soil water potential under moistube-irrigation rendering as symmetric distribution. When the use of water in irrigation is the same,the wet area is similar to the ellipse under SDI and nearly circular under moistube-irrigation and slightly larger than SDI. The uniformity of soil water distribution under SDI performed as increased-decreased periodic with irrigation-intermittent while under moistube-irrigation the uniformity of irrigation water keeping increasing and larger than SDI.