The efficiency of drip irrigation is highly dependent on evaporation losses occurring from the constantly saturated soil beneath emitters. Advent of subsurface drip irrigation is in part an approach to curb this inefficiency. An irrigation method, Sand Tube Irrigation (STI), is proposed to increase the efficiency of “Normal” surface applied drip Irrigation (NI method) on permanent tree crops without the need for burying the irrigation tubing. The sand tube consists of removing a soil core beneath the emitter and filling the void with coarse sand. A weighing lysimeter was constructed in the laboratory and instrumented to directly measure temporal evaporation from large, undisturbed soil columns, 0.7 m in diameter and 0.8 m in height. Experiments were performed on six replicated soil monoliths to compare the two methods. The results indicated that, for four consecutive days after irrigation, there was a significant difference at the 95% confidence level between evaporation occurring from the NI and STI methods. After four days of evaporation, comparison of water contents indicated that a higher amount of water existed 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 plant use rather than potential evaporation.

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Published in Transactions of the ASAE, v. 43, issue 1, p. 79-86.

© 2000 American Society of Agricultural Engineers

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The work reported in this article was supported by the Kentucky Agricultural Experimentation Station and is published with the approval of the Director as Journal Article No. 99-05-17.