Evaporation reduction potential in an undisturbed soil irrigated with surface drip and sand tube irrigation

The efficiency of drip irrigation is highly dependent on evaporation losses occurring from the constantly saturated soil beneath emitters. Advent of s ubsurface drip irrigation is in part an approach to curb this inefficiency An irrigation method Sand Tube Irrigation (STI), is proposed to increase th e efficiency of "Normal" surface applied drip Irrigation (NI method) on per manent tree crops without the need for burying the irrigation tubing. The s and tube consists of removing a soil core beneath the emitter and filling t he void with coarse sand. A weighing lysimeter was constructed in the labor atory and instrumented to directly measure temporal evaporation from large, undisturbed soil columns, 0.7 m in diameter and 0.8 m in height. Experimen ts were performed on six replicated soil monoliths to compare the two metho ds. The results indicated that, for four consecutive days after irrigation, there was a significant difference at the 95% confidence level between eva poration occurring from the NI and STI methods. After four days of evaporat ion, comparison of water contents indicated that a higher amount of water e xisted between the depths of 0.2 to 0.55 m in the STI versus the NI method. Although drainage occurred from the macropore structure of the undisturbed soil monoliths, the STI method showed potential in retaining more water in the micropore structure of the lower depths, that would be available for p lant use rather than potential evaporation.