Comparison of water and temperature distribution profiles under sand tube irrigation

Drip irrigation is one of the most efficient systems in delivering water to the plant root zone. Research has shown that the saturated, or nearly satu rated, surface beneath the emitter may increase evaporation thereby reducin g the irrigation efficiency. To increase the efficiency of surface applied drip irrigation on permanent tree crops a sand tube irrigation (STI) method was developed and tested. The sand tube method consists of removing a soil core beneath the emitter and filling the void with coarse sand. A weighing lysimeter was designed and instrumented to directly measure temporal evapo ration during irrigation and for a period of three days after irrigation ce ased. Thermocouples were used throughout the soil profile to detect the tem perature variation and also to determine temporal movement of the wetting f ront. The results indicated that for the surface applied drip irrigation me thod, approximately 30% of the applied water evaporated during the four-day period after irrigation. the STI method resulted in approximately 4% of th e applied water being evaporated. The STI method allowed more water to rema in in the soil profile thereby increasing the irrigation efficiency.