Experimental Study of the Effects of Texture and Soil Layering on the Redistribution Wetting Front from a Point Source

Wetting front (WF) and redistribution wetting front (RWF) depend on different parameters such as soil type, soil layering, land slope, and emitter discharge rate. Experiments were conducted on the physical model applying constant 24 litres of irrigation water, three different slopes (0, 10, and 20%), and three different discharge rates (2, 4, and 8 L/h). Three homogeneous soils with light, medium, and heavy textures, and two non-homogeneous soils with horizontal layers (LMH: a light texture in the top layer, a medium texture in the middle layer, and a heavy texture in the bottom layer; HML: a heavy texture in the upper layer, a medium texture in the middle layer, and a light texture in the lower layer) were used. The results showed that when the dripper flow rate doubled, in LMH soil, where the light texture was in the top layer, the amount of wetting depth was, on average, 20% higher than HML soil in which the top layer had a heavy texture. In all experiments, the highest increases in the maximum wetting depths of the RWF in five measurement stages within 24 h after irrigation were related to slopes of 0%, 10%, and 20%, respectively. A comparison between homogeneous and non-homogeneous soils showed that the change in soil layering has a significant effect on the radius and depth of wetting. This matter needs to be considered in the design of drip irrigation systems.