Study On Soil Water And Nitrogen Transport And Numerical Simulation Under Drip Irrigation

In this paper,the influence of the parameters of drip irrigation fertilization system--water,drip flow and nitrogen application concentration on the distribution of water and nitrous nitrogen transportation is analyzed,and provides theoretical reference for the design and operation of drip irrigation fertilization system.The drip irrigation infiltration test was carried out using rectangular plexi glass soil box to observe the infiltration characteristic value,soil moisture content rate and nitrate transfer distribution.The number of Mark's bottles at different times,radial and drop-down wet front distances were also monitored during the test.HYDRUS-2D was used to simulate the distribution of soil water content and nitrous nitrogen content in soil under different water fertilizer conditions.The main research contents and conclusions are as follows:(1)Under different drip irrigation fertilization conditions,the amount of irrigation and drip head flow have a greater effect on the infiltration characteristic value than the nitrogen application concentration.The larger the irrigation water,the greater the wet front moving distance,the larger the volume of the wet area.The accumulation and infiltration rate of soil under different irrigation water,drip flow and nitrogen application concentration are consistent with Kostiakov infiltration model with infiltration time.(2)The distribution of soil water content isometric map shows the characteristics of sparse upper part of wet area,small change of moisture content,dense lower part,and large change in water content.The effect of irrigation water and drip flow on soil moisture content was higher than that of nitrogen application concentration on soil moisture content.And the amount of water,drip flow and nitrogen application were positively correlated with soil moisture content.The coefficient of regressment of soil moisture content is high,and the F-test and t-test have reached significant levels,which can better simulate the change of soil moisture content under different drip irrigation and fertilization conditions.(3)The distribution of the soil's relative nitrate nitrogen content contour map shows the distribution characteristics of less than 1 in the middle of the contours of the wet area,and the edge of the wet front is greater than 1.The effect of nitrogen application concentration on soil nitrate nitrogen content is much greater than the amount of water and drip flow.And the nitrogen application concentration was positively correlated with soil nitrogen content,and the amount of water and drip flow was negatively correlated with soil nitrogen content.The coefficients of the regression equations are acceptable,and the F-test and t-test have reached significant levels,which can simulate the changes of soil nitrate nitrogen content under different drip irrigation and fertilization conditions,but the accuracy is not high.(4)Through HYDRUS-2D,the simulated value of soil moisture transfer is more consistent with the measured value,which better reflects the change law of water transfer.The analog value of nitrous nitrogen content is generally consistent with the measured value.The decision coefficient of soil moisture content and nitrate nitrogen was 0.947 and 0.731 respectively,the relative error of soil moisture content was 6%,while the soil nitrogen content was 8%,the average square root error range of soil moisture content was 0.018 to 0.029,and the average square root error range of soil nitrate nitrogen content was 0.023 to 0.0392.