Numerical modeling of soil moisture profiles under pitcher irrigation application
Edward Saleh1, Budi I. Setiawan2
(1. Sriwijaya University, Indonesia; 2. Bogor Agricultural University, Indonesia)
Abstract: Pitcher, a bottle-like irrigation emitter made of baked clayed soils mixed with sands has been recognized as the oldest traditional irrigation. It has high water efficiency since the water seeps directly into and concentrated in the root zones. Numerical and experimental studies were conducted to investigate the water flow in the soil surrounding a pitcher and to figure out the availability of soil moisture for crops. The Darcy and Richards’ equations of water flow in a cylindrical coordinate system was applied and was solved using Finite Element Method to describe soil moisture profiles. Two soil textures were used, one was silty clay and the other was sand. The hydraulic conductivity of the pitcher was in order 10-6 cm/s which was 100 times smaller than that of the two soils. The pitcher was buried in the center axis of a soil box and water was given from Mariotte tube to maintain a constant water level inside the pitcher. The results showed the infiltration rates decreased linearly rather than exponentially even though the soil was initially dry. The advancement of wetting front was very slow and somewhat limited to a radius and depth of no more than 30 cm and 40 cm, respectively for both tested soils. The surrounding soil moisture was in a range available for plant growth. Different depths of pitcher placement in the soil produced different reaching distances of the wetting front but showed insignificant differences in water availability. Accurate placement of pitcher depth in soil is important to provide effective soil wetness in the root zone and reduce evaporation rate. The right placement of pitcher must be determined based on the hydraulic characteristics of the pitcher and the soil. In this study, 5 cm placement depth of the pitcher’s shoulder is an appropriate reference for the application of pitcher irrigation.
Keywords: pitcher irrigation, infiltration rate, soil moisture profiles
Citation: Edward Saleh, Budi I. Setiawan. Numerical modeling of soil moisture profiles under pitcher irrigation application. Agric Eng Int: CIGR Journal, 2010, 12(2): 14-20.