Modeling of soil water to ensure a suitable depth and spacing of subsurface drip irrigation for alfalfa

Abstract

Introduction: A major design issue in implementing a subsurface drip irrigation (SDI) system is determining the appropriate drip tape placement depth to allow basic farming operations while still providing adequate water to the crop. Objective: To determine the appropriate placement depth of the SDI tapes using modeling techniques and classical soil mechanics theory. Methodology: The HYDRUS-2D program was used to determine the wetting pattern, after 12 h of irrigation, of a SDI emitter installed at 50 cm depth in three soil types: sandy clay loam (SCL), clay loam (CL) and loam (L), and classical soil mechanics theory was used to calculate the increase in soil stress at different depths. Results: The vertical capillary rise above the dripline was 27, 30 and 22 cm for SCL, CL and LF soils, respectively. The minimum dripline placement depth to avoid failure is 40 cm in SCL and L soils, and 35 cm for CL soil. Study limitations: The physical properties and hydraulic parameters of the soil were obtained from the literature, and the soil mechanics theory results were not calibrated with field measurements. Originality: This is the first study in which soil mechanics is used to determine the spacing and installation depth of SDI system tapes. Conclusions: This type of study is helpful in determining the SDI dripline placement depth to ensure adequate trafficability under these irrigation systems.