Study Of Sandy Soil Drip Irrigation Wetting Characteristic On Different Soil Available Water Boundaries Based On Hydrus Model

The research method in this paper is combined by indoor test and simulation test.The indoor drip irrigation is carried out in the sandy loam soil(sandy loam soil in Yangling section of Weihe Shaanxi Province).The accuracy of the model is evaluated by comparing the measured data with the simulated data of HYDRUS model.Using the HYDRUS model,the soil water movement under different irrigation elements is simulated,and the irrigation parameters(drip irrigation,irrigation layout,flow)factors on the wetting front in the horizontal and vertical distance and different boundary effects of the effective soil moist body shape,water distribution and time-variation is analyzed.The main conclusions as follows:(1)When the irrigation amount at the same time,large flow drip wetting front rapid diffusion of small flow drip irrigation by slow diffusion;at the same time,different flow emitters in drip irrigation after the wetted volume had little difference,but the distribution of soil moisture in the process,the small flow range compared to large flow drip drip diffusion more that volume is mainly a result of vertical water movement.Suffer software and Auto-CAD software are used to calculate the effective wetting volume,which greatly reduces the workload of the calculation of the effective wetting body and improves the accuracy of the calculation.And the defense law of effective wetted volume under different treatments is analyzed.When the effective wetted boundary layer is divided according to different values,the effective wetting soil with the change of time is also different.Generally speaking,when the effective wetted boundary layer is 60%~80% of field water capacity,it is the most favorable for plant absorption.According to the criterion of the minimum 60%,the smaller the dripper flow rate,the larger the volume of the effective wetted soil.(2)Regression analysis of saturated zone radius and flow relationship as the index,and it increases with the increase of dripper discharge,can be used to determine the boundary conditions of the simulation model;HYDRUS model was calibrated using the measured data,comparative analysis of wetting front and water content spatial distribution simulation and measured values,less error,high precision.(3)HYDRUS simulation software is used to simulate the change rule of actual effective wetting ratio under single point source infiltration and double point source infiltration anddifferent design conditions.And the effects of various factors on the specific moisture ratio were analyzed.The correlation analysis of the test results is carried out by using SPSS software.The results from the analysis of the variance of the actual effective wetting ratio are obtained from the flow rate of the emitter,the ratio of the planned wetting ratio,the percentage of the holding percentage and the redistribution time.The effects of dripper flow rate,the percentage of soil moisture content(the effective moisture content at the boundary of the wetted boundary),the planned humidity ratio and the duration of drip irrigation on the effective wet ratio are significant.Among them,the percentage of cropland holding had the greatest effect,and the ratio of planned wetting and redistribution is smaller,and the flow rate is smallest.Based on the item factor gradient analysis,the relationship between the dripper flow rate,the ratio of planned moisture content,the percentage of the holding percentage and the redistribution time to the actual effective moisture ratio is obtained.For sandy soil,if the moisture content of 60%~80% is used as an effective wetting boundary,the effective wetting volume is less than that of the designed wetted volume,and the effective moisture ratio is less than the design wet ratio.