Characteristic parameters of soil wetted volume under indirect subsurface drip irrigation

The steady-state principle of constant-head well permeameter, which was used to calculate the field-saturated hydraulic conductivity, was applied to quantify the suitable emitter discharge rate for indirect subsurface drip irrigation under different water-conducting device specification conditions in this text. Using the calculated emitter discharge rate to supply water, characteristic parameters of wetted soil volume were studied during the water movement process. Results indicated that the steady-state model of constant-head well permeameter could be used to design the emitter discharge rate for different water-conducting device specifications and soil types. During the infiltration process of indirect subsurface drip irrigation, the ponded water depth changed from zero to a constant and accelerated the water movement in the vertical direction, which reduced the discrepancy of wetted distance in lateral direction and vertical direction, while the changed water depth had small influence on the wetting front movement in vertical direction to upward and downward. The shape of wetted soil zone was spheroid, and its symmetry axis lied near the bottom of the water conducting device. The maximum wetted distance and volume of wetted soil zone were the function of irrigation time. The increment of average volumetric water content in the wetted zone had no relationship with irrigation time, and kept a constant during the whole irrigation process. The volume of wetted soil zone and the increment of average volumetric water content in wetted zone had relationship not only with soil types, but also with the combination between water conducting device parameters and emitter discharge.