Impact of treated wastewater on soil hydraulic properties and vegetable crop under irrigation with treated wastewater, field study and statistical analysis

Due to aridity, scarcity and unsustainably of natural water resources many developing countries tend to utilize wastewater for crop production. The use of treated wastewater in irrigation has many advantages and disadvantages to soil, crop and environment. The objective of the study was to investigate the effect of irrigation with wastewater on soil physical and hydraulic properties of soil, as well as the effect on yield, yield components and irrigation water use efficiency (IWUE) of vegetable crop grown under surface and subsurface drip irrigation systems. Field experiments were carried out over two consecutive seasons (2011 and 2012) at an agricultural field site in Saudi Arabia. A strip plot design (split block) was constructed to maintain six wastewater qualities. Crop water requirement was calculated by Penman Monteith equation for dry land condition. Physical and hydraulic properties of soil were analyzed at pre-season and post-season to quantify the impact of wastewater treatment. Results were statistically analyzed by analysis of variance and mean separation by LSD test. Post-season analysis indicates that the second layer of soil profile was affected. The saturated hydraulic conductivity decreased by 43%, alpha value increased by 6%, and n value decreased by 2%. Accordingly simulation results a reduction of cumulative flow through soil profile was observed. On the other hand, the response of vegetable crop to wastewater qualities, irrigation systems and growing seasons was different. The fruit yield and IWUE under subsurface irrigation system were significant as compared to surface irrigation system using two seasons. However, the local groundwater (LGW) practice produced highest yield and maximum IWUE; followed by qualities containing less percentage of wastewater. The statistical approach was successful in the analysis of designed experiment.