Spatial and Temporal Characteristics of Infiltration Wetting Front of Ring-Shaped Root Emitters

Abstract

Ring-shaped root emitter is a new type of emitter applicable to the roots of fruit trees in arid areas. To study the characteristics of infiltration wetting front changes in ring-shaped root emitters, the orthogonal test method was used to design nine groups of schemes for four factors: radius of irrigation ring R, burial depth H, number of orifices M, irrigation water volume V and their three levels (R = 20, 30 and 40 cm; M = 4, 6 and 8; H = 20, 30 and 40 cm, V = 40, 60 and 80 L). The infiltration process of these nine scenarios was simulated using HYDRUS-3D software. The results show that the interference infiltration time exhibited a good power function relationship with the irrigation ring radius, number of orifices and burial depth; before the interference infiltration, the wetting fronts were all in the shape of a rotating ellipsoid centered on the infiltration point and can be expressed by the equations of the upper and lower semi-elliptic curves relative to the infiltration point. With the increase in time, the wetting fronts were centered at the infiltration point and infiltrated in all directions at a different velocity. The transport rate decreased with time. The power function relationship between the wetting fronts and the influencing factors after the interference infiltration in different directions was established, and the coefficient of determination was above 0.888. The wetting front shape after infiltration stabilization can be regarded as a rotating body formed by the vertical wetting front plane around the z-axis. The wetted soil volume of deep percolation, surface and suitable infiltration scenarios was rugby-shaped, apple-shaped with a flattened top and complete apple-shaped, respectively. Burying the irrigation ring at slightly deeper than one-third of the crop root zone is recommended, and half of the horizontal range of the crop root system can be selected as the irrigation ring radius. The research results can provide a reference for selecting root emitter parameters and layout as well as developing a root irrigation system.