THE DISTRIBUTION OF POTASSIUM AND SODIUM BETWEEN THE SOLUTION AND THESOLID-PHASE IN A TERNARY (K-NA-CA) SYSTEM

Reduction of sodicity hazards in soils irrigated with waste water can be achieved through the replacement of the Na salts (mainly NaCl), use d in water softening and other industrial processes, with potassium sa lts. We studied the effect of equilibrating a grumusol (Typic Chromoxe rert) with solutions of differing potassium adsorption ratio (PAR) and sodium adsorption ratio (SAR), within the range expected in waste wat er, on the distribution of K and Na between the solution and the solid phase. The K distribution did not depend on the level of Na in the so lution, but the distribution of Na between the 2 phases depended stron gly on the PAR of the solution. For SAR 10 solutions, ESP decreased fr om 11.1 to 7.8 as PAR increased from 0 to 4. Gapon selectivity coeffic ients for Na, calculated separately for each PAR level, also decreased with increasing PAR. The Na distribution between solution and solid p hase in a ternary (K-Na-Ca) system could not therefore be predicted fr om the Gapon selectivity coefficient obtained from a binary (Na-Ca) sy stem.