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A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m3 ha-1 water applied, and the minimum water saving was obtained using FI with 6822 m3 ha-1. The predicted irrigation water requirements using the Penman�Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m3 ha-1. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 103 kg ha-1) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 103 kg ha-1). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m-3) and the minimum was obtained with the FI method (1.43 kg m-3). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.
