Sodium removal from a calcareous saline–sodic soil through leaching and plant uptake during phytoremediation

Abstract

Abstract Saline–sodic and sodic soils are characterized by the occurrence of sodium (Na + ) to levels that can adversely affect several soil properties and growth of most crops. As a potential substitute of cost‐intensive chemical amelioration, phytoremediation of such soils has emerged as an efficient and low‐cost strategy. This plant‐assisted amelioration involves cultivation of certain plant species that can withstand ambient soil salinity and sodicity levels. It relies on enhanced dissolution of native calcite within the root zone to provide adequate Ca 2+ for the Na + Ca 2+ exchange at the cation exchange sites. There is a lack of information for the Na + balance in terms of removal from saline–sodic soils through plant uptake and leaching during the phytoremediation process. We carried out a lysimeter experiment on a calcareous saline–sodic soil [pH of saturated soil paste (pH s ) = 7.2, electrical conductivity of the saturated paste extract (EC e ) = 4.9 dS m −1 , sodium adsorption ratio (SAR) = 15.9, CaCO 3 = 50 g kg −1 ]. There were three treatments: (1) control (without application of a chemical amendment or crop cultivation), (2) soil application of gypsum according to the gypsum requirement of the soil and (3) planting of alfalfa ( Medicago sativa L.) as a phytoremediation crop. The efficiency of treatments for soluble salt and Na + removal from the soil was in the order: gypsum ≈ alfalfa > control. In the phytoremediation treatment, the amount of Na + removed from the soil through leaching was found to be the principal cause of reduction in salinity and sodicity. Copyright © 2003 John Wiley & Sons, Ltd.