Effect of Detergents from Greywater on Irrigated Plants: Case of Okra (Abelmoschus esculentus) and Lettuce (Lactuca sativa)

Laundry detergent containing anionic surfactants was used to test their effects on plant growth through irrigation water. Lettuce and okra were cultivated in pot experiment and irrigated with distilled water containing domestic detergent at three different concentrations: low concentration (LC) of 0.1 g L-1; normal concentration (NC) of 1.0 g L-1 and high concentration (HC) of 5.0 g L-1 and distilled water (DW) used as control. The experiment was conducted during three months from July to October in a green house in Ouagadougou, Burkina Faso. Lettuce leaves, okra fruits and both crops shoots were measured at harvest period as dry and/or fresh weights. Soil pH and electrical conductivity (EC) were analyzed to evaluate changes caused by watering. Soil pH and EC tended to increase with detergent concentration in irrigation solutions. They were no significant difference in okra’s fruit growth (fresh and dry weight) for DW, LC and NC treatments. However plants in HC died 20 days after planting (DAP). Similarly, no significant difference was noticed in lettuce shoots (dry weight) between LC, NC and DW treatments but lettuce in HC died 12 DAP. After harvest, irrigated soils EC for all treatments were significantly increased in contrast to pH where no significant difference was obtained.The study show that more than 1.0 g L-1 of laundry detergent can inhibit plant growth and application of high concentrate greywater on detergent can exacerbate soil salinity.