Seawater intrusion and crop response to salinity in coastal Lebanon

ABSTRACT

Research conducted between 1999 and 2004 to assess pressure on coastal zone focused on three main objectives: first, the evaluation of seawater intrusion in southern coastal wells, second, the soil salinization in greenhouses irrigated by well waters, and third the management of saline water in two soil textures. Groundwater contamination was assessed by regular sampling of six wells for 30 months. The salinity of water fluctuated around 3 dS m[-1] and the Simpson index [Cl/HCO[3]] indicated levels of moderate to injurious contaminations. The Na/Cl ratios remained < 1, suggesting a seawater intrusion rather than an anthropogenic origin. In all sites, greenhouse growers had to rely on other water sources [e.g. rainwater, domestic] to supply the crop needs. In some cases, the crop had to be interrupted as salinity decreased yields. Improving the management of water and nutrients was studied in a tomato/Jew's-mallow sequence. Three levels of water salinity [1, 2.5 and 5 dS m[-1]] were tested in sandy and clay soils. Under sound management of fertilizers input and a leaching fraction, the salinity had no obvious negative effect on tomato in the clay soil. The Jew's mallow had a role in the removal of residual salts.