Investigation of Moisture Distribution in Subsurface Drip Irrigation and Comparison of the Data with HYDRUS-2D Results

Moisture distribution is one of the most important factors in selecting the suitable irrigation method for a crop. In this study, distribution of soil moisture content in sugarcane subsurface drip irrigation in silty-clay soil, was investigated. The experiments were carried out with drippers having the discharge rate of 1.2 liter per hour, three installation depths of 15, 20 and 30 centimeters (d15, d20, d30), and two spaces of 50 and 60 centimeters (L50 and L60), at three replications. Soil water content sampling during the experiment was performed at the three stages with three horizontal distances of 0, 30 and 60 cm from the drip pipe and at depths of 0-30, 6-30 and 90-60 cm, respectively. Using HYDRUS-2D, moisture distribution around the supply pipes installed at three depths in the condition of 60 cm distance between the drippers, was determined. To evaluate the accuracy of HYDRUS, the moisture content was measured by TDR device at 15 observation points around supply pipe. The moisture content around the supply pipe within the horizontal distance of 60 cm and the vertical distance of 90 cm was within range of wilting point and field capacity. Accuracy of HYDRUS-2D software in simulation of soil moisture around the supply pipe for condition of 60 cm distance between the drippers at the depths of d15, d20, and d30 based on the NRMSE criterion, were in the medium, good and medium range, respectively.