Impact of Initial Soil Water Content on Infiltration of Irrigation Water in Aeolian Sandy Soil

【Objective】 The movement of irrigation water in soil is an important parameter in irrigation design. It is affected by many factors. This paper investigates the impact of initial soil water on infiltration of subsurface irrigation water in an aeolian sandy soil. 【Method】 The outdoor experiment was conducted in tanks repacked with the sandy soil, with the initial soil water content controlled at 5.1%, 11.5%, 16.8%. The movement of the wet zone in each treatment was monitored visually. Infiltration processed was simulated by different analytical models. 【Result】 The wet zone in all treatments was approximately elliptical, with the center located at the perfusion pipe. Increasing initial soil water content accelerated the movement of the wetting front but reduced the cumulative infiltration amount and infiltration rate. The cumulative infiltration amount increased with infiltration time in a power-law function, and the infiltration index increased with the initial water content. Comparison with measured data revealed that the R2 of the Kostiakov model, Philip model, empirical model and Horton model was 0.783, 0.785, 0.923 and 0.943, respectively. When the initial water content was 5.1%, 11.5% and 16.8%, the burial depth of the irrigation pipe should not exceed 10, 20 and 30 cm, respectively, and the associated pipe spacing not exceed 30, 60 and 90 cm, respectively. 【Conclusion】 Increasing initial soil water content in aeolian sandy soil allows the irrigation pipes to be buried deeper and spaced widely. These findings are helpful for designing subsurface irrigation in aeolian sandy soil which is common in northwestern China.