Potential of dry drainage for controlling soil salinity

Abstract

The primary aim of this paper is to discuss the concept of "dry drainage," i.e., drainage by evaporation from fallow areas, as a possible technique for controlling soil salinization. The technique requires retirement to be imposed on a part of the irrigated land. The remainder of the land is used for crop production. While the retired area is unirrigated, normal irrigation practices are carried out on the remaining area. For the technique to be effective, it is essential that a shallow water table and high evaporation rates are present. These conditions are the characteristics of arid and semi-arid regions. A field-scale test of a dry drainage unit is illustrated numerically using a field-scale model and field-scale data from the San Joaquin Valley of California, U.S.A. It has been shown that it is possible to obtain an optimal land-use pattern for a dry drainage scheme that satisfies the design requirements. However, some limiting factors that influence the design have to be considered. These are related to the soil properties, the practiced crop, climatic conditions, and economic factors.Key words: salinity, drainage, leaching requirements, saturated and unsaturated zones, evaporation, mathematical modelling.