Causal processes of soil salinization in Tunisia, Spain and Hungary

Soil salinization arises due to the build up of soluble salts at or near th e soil surface. Salts accumulate by primary and secondary processes that al ter the soils physicochemical properties and lead to direct and indirect so il degradation. Results are presented here from the study of three contrast ing salt-affected landscapes. The Chott el Fedjadj, Tunisia, is a naturally salt-affected basin containing saline sediments deposited during a marine incursion. The endoreic conditions lead to salt recirculation, concentratio n and reprecipitation. In the Guadalentin Valley, Spain, increased irrigate d agriculture has led to aquifer overexploitation releasing gas and salts. Irrigating with the resultant contaminated groundwater has induced soil sal inization. The salt accumulation and translocation is dictated predominantl y by irrigation method, water quality and quantity. Hungary has the largest expanse of naturally salt-affected soil in Europe, with the dominant soil type being solonetz. In Hungary the type of salt-affected soil development is related to the salts present, hydraulic properties of the soil and depth and quality of the watertable. In Tunisia a catenary relationship of incre ased water and soil salinity towards the centre of the chott is found, wher eas in Spain the highest salinities were found under flood irrigation with the valley displaying a complex spatial distribution of soil salinity. The sediment distribution in Hungary dictates that solonchak soils are found mo stly in the Danube-Tisza interfluve and solonetz soils in the Tisza floodpl ain, with localized variations in soil type related to watertable character istics. Copyright (C) 2001 John Wiley & Sons, Ltd.