Soil-wetting front in surface and subsurface drip irrigation

Abstract

Surface and subsurface drip irrigation systems have been applied to increase irrigation efficiency and uniformity, mainly in arid and semi-arid regions. Determining soil-wetting dimensions around a point source emitter is essential for better design of drip irrigation systems. Laboratory experiments were thus conducted to measure the soil-wetting front for various arrangements of surface and subsurface drip irrigation in terms of emitter number, installation depth and flow rate. The two-dimensional numerical model Hydrus-2D was used to simulate water movement around the emitter(s) in silty loam soil. The shapes of observed and simulated soil-wetting front were almost ellipsoid and spherical for surface and subsurface drip irrigation respectively. The 2D model proved better at estimating the dimensions of the soil-wetting front when using one emitter than when using two emitters for irrigation. Both simulations and observations indicated that wetting velocity was greater during irrigation than during soil moisture redistribution. The model under- and overpredicted wetting area during irrigation and redistribution respectively, but there were no significant differences between measured and predicted values of wetting area for surface and subsurface drip irrigation. The model generally proved effective in simulating soil water flow for various kinds of surface and subsurface drip irrigation systems in silty loam soils.