Soil Water Dynamics Under Drip Irrigation: Transient Flow and Uptake Models
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Advances in drip irrigation management rely on knowledge of the distribution and dynamics of soil water within the wetted soil volume. Part of the information can be obtained from numerical or analytical models for water flow from point or line sources. However, a more complete picture of soil water dynamics in cropped fields requires explicit consideration of plant water extraction patterns. In this study we propose to combine an analytical solution for transient flow from cyclic point sources representing drippers with a parametric model for uptake by plant roots. The linearized flow and uptake problems are amenable for spatial superposition. The transient uptake pattern is represented by an array of buried line sinks of different strengths determined by a new parametric uptake model. In addition, a point approximation is proposed (for monitoring purposes) based on a localized water balance which considers changes in water content due to transient flow from the dripper coupled with plant uptake only from the soil volume under consideration. Comparisons with greenhouse (and field) measurements show very good agreement with the localized approximation for one- and two-day irrigation intervals. The superposition solution of point source with an array of line sinks tended to under-estimate uptake. The two methods offer reasonable means to describe soil water dynamics within wetted soil volumes under cropped conditions for various irrigation management scenarios.