Irrigation with wastewater is a widespread observable fact in developing countries, especially
those exhibiting arid climate conditions. Utilization of large volumes of domestic wastewater effluent
is part of an overall integrated water resources management. The objective of this study was to
investigate the effect of irrigation by six different treated domestic wastewater qualities on the yield of
Cabbage and Lettuce crops under surface and Sub-surface drip irrigation systems. Field experiments
were carried out during 2011 and 2012 seasons at the Agriculture Research station of King Abdulaziz
University located at Hada Alsham area north east of Jeddah city. The six water qualities were
prepared by diluting treated wastewater with local groundwater of the region. The dilution
percentages were 0%, 20%, 40%, 60%, 80%, and 100% treated wastewater. Crop water requirement
were calculated based of Penman Monteith equation for dry land condition and supplied daily to the
crops. The obtained results showed significant impact of wastewater quality and irrigation system and
their interactions on vegetative yield and yield components of both crops. Irrigation with 60% and
80% wastewater under sub-surface irrigation system produced the highest yield and yield components
in both seasons. Irrigation Water Use Efficiency (IWUE) of cabbage crop increased under the use of
subsurface drip irrigation while IWUE of lettuce crop increased under surface drip irrigation system.
Among dilution percentages, the 60% gave the highest IWUE in both crops. In conclusion, this study
implies an advantage of using treated wastewater in growing vegetable crops. This in turn saves
considerable quantities of local groundwater resource.