Groundwater irrigation induced soil sodification and response options

Abstract

The continuous surge in irrigation, particularly using groundwater for sustaining food security in many developingc countries, has necessitated the utilization of low-quality waters especially in water-scarce arid and semiarid regions. Inappropriate irrigation with these waters results in land and environment degradation produced by associated salts, sodium and other toxic elements. Generally the soil’s sodification process is insidious and build-up of exchangeable-Na is initially gradual. It stabilises at levels governed by sodicity indices of irrigation water, soil type, cropping sequences and agro-climatic conditions. As the soils become sodic, crop productivity declines and ultimately soils can become unsuitable for cropping. As a result, cultivators are forced to opt for tolerant crops, which are typically of less economic value. To minimize harmful effects of sodicity, remedial measures have been developed at the crop, root zone, farm and district/basin levels. These include water quality driven conjunctive uses, chemical amelioration of soils and irrigation waters, mobilising native calcite through phyto-remediation, growing tolerant crops, and other specialised tillage, fertiliser use and irrigation practices. This review seeks to critically analyse the role of these measures and the crop, water and soil factors defining the sodification vis-à-vis infiltration problems. The conclusions provided here are expected to be helpful for a range of stakeholders to promote irrigation with sodic/alkali waters, thereby partly alleviating the forecasted scarcities in water for agriculture.