A smart capillary barrier-wick irrigation system for home gardens in arid zones

New water-conserving irrigation technologies are vital in arid countries. We investigated the effects of (i) soil substrates made of Smart Capillary Barrier Wick (SCB-W), consisting of silt loam blocks surrounded by sand-sheathes and irrigated with a sand wick cylinder (WC) as compared to a control (homogenous soil irrigated by the same wick system, HW), (ii) WC diameters (2.54 cm vs. 1.27 cm), and (iii) 2-cm sand mulch layer on soil–water dynamics during wetting–drying cycles. Field experiments with pots and HYDRUS (2D/3D) modeling were performed in two consecutive phases (with and without sand mulch). Analysis of variance at p < 0.05 was used to assess significant differences in measured water contents, θ, between the two substrates. For the wetting/drying cycles, the modeled and measured θ are in satisfactory/tolerable agreement, as documented by the model evaluation criteria, which are within acceptable ranges (the root mean squared error, RMSE 0.01–0.06; Nash–Sutcliffe coefficient, NSE 0.51–0.97, and Willmott index, d = 0.97–1). SCB-W wets the soil substrate about two times faster than HW during the wetting cycles (p < 0.05). Reducing the WC diameter prolonged the wetting time by 1 and 2 days for SCB-W and HW, respectively, the same trend of two times faster wetting of SCB-W compared to HW was maintained. SCB-W showed higher θ storage (by 44.3–52.4%) at the bottom part of the composite than HW (p < 0.05). The sand mulch layer reduced evaporation and resulted in 20 and 38.9% higher θ during the drying cycle for both the bottom and top sensors, respectively, in both substrates (p < 0.05). SCB-W could improve water conservation in home gardens.