Study of the Expansion of Wetting Front from a Point Source in Vertically and Horizontally Layered Soils

Land slope, soil texture, emitter flow rate and volume of irrigation water are among the main factors that influence the shape of the wetting front in the soil. The experiments were conducted in four different groups of heterogeneous three-layered soils, two of which were horizontally layered and two vertically layered, at three slopes (0, 10 and 20%) and three emitter flow rates (2, 4 and 8 L/h) with a constant volume of irrigation water (24 L). The results revealed that the maximum value of the wetting front radius in the experiments varied from 33 to 109 cm whereas the values for the wetting front depth under the emitter were in the 39-71 cm range. The highest increase in the maximum wetting front radius belonged to the horizontally layered soil with the heavy layer at the top. The wetting front depth under the emitter slightly decreased with increases in slope. The maximum infiltration depth was that of the vertically layered soil with a light-textured middle layer and heavy-textured top and bottom layers. When other conditions were kept constant, the percentage of the wetted area Was decreased with increases in the emitter flow rate. The highest percentages of the wetted area downstream of the emitter varied from 74 to 78 percent at flow rate of 8 L/h and 20% slope.