Effect of Dilution on Calcium and Potassium Contents of Soil Solutions1
- F. E. Khasawneh and
- Fred Adams2
The effect of dilution on the composition of a soil solution of Magnolia sandy clay loam subsoil was investigated. Samples of a Ca- and K-saturated soil as well as samples of a soil saturated with K and mixed with CaCl2 were equilibrated with water in various soil-water ratios. Equilibrium solutions were separated and analyzed for Ca and K. Dilution increased the total amount of solution electrolytes with a concurrent change in the relative amount of each of the solution cations. The following equation was derived from Langmuir's isotherm to describe the desorption of neutral salts from soil surfaces: S = St V/(a + V) where S is the total meq of solution cations in volume V ml, and St and a are constants.
The ratio-law of Schofield was adequate to describe the change in the relative amount of each cation upon dilution of one soil system, but a correction term was added to the formulation of the ratio-law in order to describe the data of the other soil system. This formulation of the ratio-law is given as where m is the number of solution mmoles, V is the solution volume in ml, and k and h are constants. The two foregoing equations provide the means for predicting the composition of a soil solution upon dilution.
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