Amelioration strategies for saline soils: a review

Soil salinization is one of the major causes of declining agricultural productivity in many arid and semiarid regions of the world. Excessive salt concentrations in soils, in most cases, cannot be reduced with time by routine irrigation and crop management practices. Such situations demand soil amelioration. Various means used to ameliorate saline soils include: (a) movement of excess soluble salts from upper to lower soil depths via leaching, which may be accomplished by continuous ponding, intermittent ponding, or sprinkling; (b) surface flushing of salts from soils that contain salt crusts at the surface, a shallow watertable, or a highly impermeable profile; (c) biological reduction of salts by harvest of high‐salt accumulating aerial plant parts, in areas with negligible irrigation water or rainfall available for leaching; and (d) amelioration of saline soils under cropping and leaching. Among these methods, cropping in conjunction with leaching has been found as the most successful and sustainable way to ameliorate saline soils. Cropping during leaching or between leachings causes an increase in salt‐leaching efficiency because a decrease in soil water content occurs under unsaturated water flow conditions with a concurrent decrease in large pore bypass and drainage volume. Consequently, anaerobic conditions in soil may occur during leaching that can affect crop growth. Thus, in addition to the existing salt‐tolerant crop genotypes, research is needed to seek out or develop genotypes with increased tolerances to salinity and hypoxia. Since salt leaching is interacted by many factors, evaluation of the traditional concepts such as the leaching requirement (LR), the leaching fraction (LF) and the salt balance index (SBI) demands incorporation of a rapid, efficient and economical way of monitoring changes in soil salinity during amelioration. Besides this, numerous models that have been developed for simulating movement and reactions of salts in soils need evaluation under actual field conditions. Copyright © 2000 John Wiley & Sons, Ltd.