Assessment of soil salinity and sodicity under canal-irrigated agriculture in arid region

Abstract:

Canal-irrigated agriculture in the arid and semi-arid zones of Central Asia has lifted production in the short term but left behind a trail of secondary salinisation and sodicity that now affects almost 4.3 million hectares across the region. This research assessed the current status of soil salinity and sodicity in a 240-hectare canal command area of the Syrdarya province of Uzbekistan, where canal irrigation was introduced in 2008. Soil samples were collected from 80 grid cells on a regular 250 × 300 m pattern at three depths (0-30, 30-60, 60-90 cm) during December 2022. Electrical conductivity, pH, exchangeable sodium percentage, calcium, magnesium, sulphate and chloride were measured along with textural class. Mean electrical conductivity at the surface layer had risen from 0.84 dS m⁻¹ in 2012 to 2.94 dS m⁻¹ in 2022, a 3.5-fold increase over a decade. Exchangeable sodium percentage at 0-30 cm averaged 14.8 per cent, placing 32 per cent of the area under sodic or saline-sodic class. Tail-end cells carried 1.8 times higher salinity than head-reach cells, reflecting poor drainage and over-irrigation. The research identifies a clear need for integrated salinity management in this command area and offers a baseline dataset for future monitoring.