Disposal of drainage water: Recycling for irrigation in semi-arid regions

In arid and semi-arid regions, effluent from subsurface drainage is often saline and in the absence of a natural outlet, its disposal is a serious environmental threat. A field experiment was conducted for 7 years using drainage water of different salinity levels (ECiw = 6, 9, 12 and 18.8 dS/m) for irrigation of wheat during the dry winter season. The objective was to find if crop production would still be feasible and soil salinity would not be increased unacceptably by this practice. The experimental crop was wheat during the winter season and pearl-millet and sorghum in the rainy season,grown on a sandy loam soil provided with subsurface drainage system. All crops were given a pre-plant irrigation with non-saline canal water and subsequently, saline drainage water of different salinity levels was used For the irrigation of wheat as per the treatment. On an average, use of diluted drainage water of 6, 9,12 and 18.8 dS/m salinity levels for 6 yeats resulted in 3.3, 10.0, 16.7 and 21.7 percent reduction in wheat grain yield, respectively. Pearl-miller and sorghum yields decreased significantly only where 12 dS/m or higher salinity water was applied to previous wheat crop. Most of the salts accumulated during the winter season were leached out To safe levels by monsoon rains before the next wheat season.