Field Evaluating of Wetting Pattern from Surface Drip Irrigation System for Sand and Sandy Loam Soils

Abstract

Water distribution through soils from trickle source is very important issue since it affects irrigation efficiency, wetted surface area and wetted soil profile. Many attempts to determine wetting pattern under drip irrigation using mathematical and numerical models were carried out. The verification of the validity of which model will be suitable for Iraqi soils need a detailed study. In this paper, the field work measurements of wetted pattern in two Iraqi soils (sand and sandy loam) were conducted to investigate the validity of the application of wetting pattern formulas predicted by Dawood (2016), Amin and Ekhmaj, (2006) and Schwartzman and Zur (1986). The work was divided into two parts: the first one was the laboratory work of soil texture, field capacity, permanent wilting point, and soil porosity. The second one includes field operations through landing, installation of trickle irrigation system, installation of equipment’s and sensors, adjustment of emitter discharge by the valve on the supply pipe. In each run, initial water content was measured and the system was operated for three continuous hours with three different discharges, discharges were selected as 1, 3 and 6 l/hr. the wetted diameter and depth were recorded hourly during each run test .The field measurements of wetted area were compared with that predicted by the previous studies. The obtained result indicate that the value of the wetted diameter and depth increase with increasing of water contents, the wetted diameter are inversely proportional was saturated hydraulic conductivity, and the wetted depth was directly proportional to the saturated hydraulic conductivity. Amin and Ekhmaj 2006 formula was suitable for wetted depth in sandy loam soil with average error 13.40% and Schwartzman and Zur, 1986 formulas gave a good prediction for wetted diameters with average error 12.79% for same soil. Finally Dawood (2016) formulas were more suitable than others for sand soil with average error for wetted diameter and depth 11.49%, 16.79% respectively.