sustainable irrigation scheduling: effects of saline water on soil physical properties

In the Mediterranean environment characterized by hot, dry summers, since 1988 soil salinity research has been carried out on a clay loam soil classified as Haplustolls. Irrigation took place with commercial NaCl in solution at five levels: 0 gNaCl l-1; 1.25 gNaCl l-1; 2.5 gNaCl l-1 ; 5 gNaCl l-1 and 10 gNaCl l-1 on spring-summer vegetable crops. Three irrigation-intervals of 2, 5 and 10 days were studied. On the extreme treatments of 0% and 1% of NaCl and with 2- and,10-day irrigation frequency, soil samples were taken in duplicate at depths of 0-10 and 20-30 cm. The water retention, h(theta), and the unsaturated conductivity K(h) characteristics were measured for each sample and the parameters of the van Genuchten functions determined. Significant differences on the h(theta) and K(h) curves were observed. The h(theta) curve of the 1% treatment in both irrigation frequencies had lower values of (theta) than the 0% treatment at the same pressure head. The K(h) curve at the same pressure head considered for the h(theta), also showed a lower value for the 1% treatment than on the 0% treatment. Significant differences were observed between the mean values of most of the van Genuchten's parameters, particularly between the (O%;2 days) and (1%;2 days) treatments.