Abstract
Saline-sodic/sodic soils need soluble Ca"+for replacing adsorbed Na' during their reclamation. Low cation exchange capacity (CEC) of soils could be a rate limiting factor for Na' -Ca"+exchange in saline-sodic soils of Pakistan. Hence an increase in soluble Ca"+might not result in a proportionate increase in the Na+-Ca"+exchange and soil amelioration. Calcium chloride was added to canal water to obtain 6, 12 and 18 mel,", and to brackish water (EC=2 dS m', SAR=10) to obtain 6 and 18 mel," concentration ofCa"+.The volume of the applied solutions was equal to 3 times ofthe saturation percentage of 10 kg of strongly saline-sodic soil filled in glazed pots (EC=27 dS m', SAR=141.2), after infiltration of which leachates were collected and analyzed. The SAR and Na' concentration of leachate decreased to about 50 % of those in the"original soil with all the Ca" levels applied. The me of Na' leached per me Ca"+added were 28.7,13.5,8.9,29.8 and 7.9 for the Ca"' concentration as me L 1 of 6, 12 and 18 in canal water and 6 and 18 in brackish water, respectively. A similar decrease in sodium adsorption ratio (SAR) of the post-experiment soil and leachates by all the treatments indicated lower Ca"+in irrigation water to be better for soil amelioration than its higher concentration. Key words: Ca"'in irrigation water, saline-sodic soils
