Numerical Simulation of Water Distribution with Uptake Root in Drip Irrigation using Different Soil Hydraulic Models

Surface drip irrigation is one of the most conservative irrigation techniques that help control providing water directly on the soil through the emitters. It can supply fertilizer and providing water directly to plant roots by drippers. One of the essential needs for trickle irrigation nowadays is to obtain more knowledge about the moisture pattern under the trickling source for various types of soil with various discharge levels with trickle irrigation. Simulation numerical using HYDRUS-2D software, version 2.04 was used to estimate an equation for the wetted area from a single surface drip irrigation in unsaturated soil is taking into account water uptake by roots. In this paper, using two soil types were used, namely sandy loam and clay loam, with three types of plants; (corn, tomato, and sweet sorghum). The soil wetting pattern was analyzed each half an hour for three hours of irrigation time and three initial soil moisture content. Equations for wetted radius and wetted depth were predicted and evaluated by utilizing the statistical parameters for the different hydraulic soil models (Model Efficiency (EF) and Root Mean Squares Error (RMSE)). The values RMSE does not exceed 0.40 cm, and EF is greater than 0.96 for all types of soil. These values were between the values obtained from program HYDRUS-2D and the values obtained from formulas. This shows that evolved formula can be utilized to describe the soil wetting pattern from the surface drip irrigation system. The relative error for the different hydraulic soil models was calculated and compared with Brooks and Corey's model, 1964. There was good agreement compared with different models. RMSE was 0.23 cm, while the relative error -1% and 1 for EF for wetted radius.

Establishment and verification of the prediction model of soil wetting pattern size in vertical moistube irrigation

To solve the difficulty of observing the soil wetting pattern of vertical moistube irrigation, the HYDRUS-2D software is used to simulate wetting pattern data under different conditions. Based on the analysis of Origin 9.0 and summarizing the law of simulation data, an empirical model for predicting wetting pattern size is constructed, with the reliability of the model verified by experimental data. The results show that the power function is used to fit the relationship between the size of wetting pattern and irrigation time. The power function exponent has small changes in three directions (vertical upward, horizontal, and vertical downward) of the moistube. Further analysis shows that the power function coefficient is in accordance with the power function relationship with soil-saturated hydraulic conductivity, the steady permeability of the moistube, and the difference between soil-saturated moisture content and initial moisture content. The average absolute error of statistical indicators of the built model is between 0.30 and 1.42 cm, the root mean square error is between 0.42 and 1.65 cm, and the Nash–Sutcliffe efficiency coefficient is not less than 0.93. The model has a good prediction effect and can provide a scientific basis for the design, operation, and management of the moistube irrigation engineering.