Study On The Relationship Between The Soil Wetting Uniformity And Drip Irrigation Parameters

Drip irrigation soil moisture uniformity is a very important parameter in the design of drip irrigation, itis influenced by the irrigation parameters such as dripper discharge and dripper spacing. At present, themainly methods to research drip irrigation soil moisture uniformity is stay on the experimental stage. Basedon the basic principle of soil water dynamics, through numerical simulation and physical experiments, thispaper discussed the the relationship between the soil moisture uniformity and drip irrigation parameters.The main results are:(1) Under the condition of point source drip irrigation, according to the principle of water balanceand Darcy’s law, based on Green-Ampt and Warrick model, this paper established the mathematical modelto evaluate the soil wetted pattern in the design of drip irrigation system. The model shows that, under thedesign depth Zfand the design width Xf, in order to get high moisture uniformity, the dripper dischargeshould be decided by moist front movement time t, and it has a direct proportion relationship with t0.5. Thenthe experiment to verify the model was worked on tight sand and sandy loam. The result shows, the dripirrigation soil moist area shape under the point source which is simulated by the model and the measuredresults are in good agreement, and the calculating process is simple, the model is reliability.(2)For linear source drip irrigation, assumed that soil moisture content accdording to lineardistribution and without surface ponding, this paper established the mathematical model of the dripperspacing and soil moisture uniformity. This model reflects that dripper spacing is depending on the designwidth Xf. In order to get high moisture uniformity between two dripper, the dripper spacing Se keep apositive relationship with design width Xf. Under certain circumstances of Xf, the soil moisture uniformityCu keep a linear negative correlation relationship with the dripper spacing Se, the wider the dripper spacingand the smaller the soil moisture uniformity. Then the feasibility of the mathematic model was verifiedthrough the physical experiment about the tight sand and sandy loam.(3) Under the condition of soil surface ponding, according to the principle of water balance, a modelwas developed based on the principle of water balance and the Kostiakov infiltration equation. The modelreflects that the radius of the soil surface ponding keep direct proportion relationship with tα/2; the movingspeed of the surface ponding was subject to the soil infiltration index; the initial surface ponding wassubject to the dripper discharge. The drip irrigation experiments for validating surface ponding were carriedout on tight sand and sandy loam, the results indicate that the model can simulate the movement of soilsurface ponding under clayed soil.(4) Under the condition of linear source drip irrigation with surface ponding, this paper established themathematical model of the dripper spacing, dripper discharge and the soil moisture uniformity. The modelreflects that dripper spacing keep a positive linear correlation with the width of the soil wetted pattern andthe radius of surface ponding. Under certain circumstances of Xfand r, the soil moisture uniformity Cukeep a negative linear correlation relationship with the dripper spacing Se, the wider the dripper spacingand the smaller the soil moisture uniformity. The mathematical model which had been established about dripper discharge q reveals that determining the dripper discharge should consider the soil wetted width,wetted depth, surface poning, migration velocity of surface ponding, vertical infiltration velocity andhorizontal infiltration velocity.