STRATEGY FOR LONG-TERM USE OF SALINE DRAINAGE WATER FOR IRRIGATION INSEMIARID REGIONS

In arid and semi-arid regions, effluent from subsurface drainage is of ten saline and in the absence of a natural outlet, its disposal is a s erious environmental threat. A field experiment was conducted for 7 ye ars using drainage water of different salinity levels (ECiw=6, 9, 12 a nd 18.8 dS/m) for irrigation of wheat during the dry winter season. Th e objective was to find whether crop production would still be feasibl e and soil salinity would not be increased unacceptably by this practi ce. The experimental crop was wheat during the winter season and pearl -millet and sorghum in the rainy season, grown on a sandy loam soil pr ovided with subsurface drainage system. All crops were given a pre-pla nt irrigation with non-saline canal water and subsequently, saline dra inage water of different salinity levels was used for the irrigation o f wheat as per the treatment. On an average, the mean yield reduction in wheat yield at different ECiw was 4.2% at 6, 9.7% at 9, 16.3% at 12 and 22.2% at 18.8 dS/m. Pearl-millet and sorghum yields decreased sig nificantly only where 12 dS/m or higher salinity water was applied to previous wheat crop. The high salinity and sodicity of the drainage wa ter increased the soil salinity and sodicity in the soil profile durin g the winter season, but these hazards were eliminated by the subsurfa ce drainage during the ensuing monsoon periods. The results obtained p rovide a promising option for the use of poor quality drainage water f or the irrigation of winter wheat without undue yield reduction and so il degradation. (C) 1998 Elsevier Science B.V. All rights reserved.