In-situ Measurement of Unsaturated Hydraulic Conductivity Function by a New Point Source Field Dripper Method (NPSFDM)

Abstract

Unsaturated hydraulic conductivity function (Kh) is an important soil parameter for drip irrigation design. There are many laboratory and in-situ measurement methods available for the measurement of Kh with associated limitations. A point source field dripper model (PSFDM) using Wooding [1] theory was used by Shani et al. [2] for Kh measurement in the field for the first time. Warrick (1985) gave an approximate equation for Kh estimation. Keeping the difficulty of detecting interface and steady state conditions a new model for in-situ measurement of Kh was developed. An experimental set up (micro-irrigation simulator) was developed for in-situ measurement of Kh which simulates real field drip conditions. Steady state saturated fronts diameters were measured against 2.02, 4.04, 7.56 and 8.31 lph dripper discharges maintaining one atmospheric pressure in drip line. Ks values calculated by PSFDM-Shani, PSFDM-Warrick and PSFDM-New were 3.60, 4.31 and 3.22 cm/hr and α as 0.1643, 0.1544 and 0.1468 cm-1, respectively. Ks values measured by PSFDM are quite close to each other. Ks value measured by using inverse auger hole method (IAHM) was 0.60 cm/hr and by infiltrometer method (IM) as 0.79 cm/hr. The PSFDM is the only method available to measure any change in Kh value due to tillage or any other interventions. Newly developed experimental set up in combination to PSFD Models is the best combination for field application.