Sung-ho Lai

Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Plants, Soils, and Climate


J. J. Jurinak


A mathematical model was developed to predict the exchange of one cation by another in a soil column undergoing one dimensional cation solution displacement under steady state flow conditions. The model allowed prediction of both the solution and exchanger phase concentration of the cation in question.

The model consists of a material balance equation which is a parabolic type partial differential equation. The assumption was made that equilibrium was reached instantaneously between the cations in the solution phase and the exchanger phase. This assumption reduced the material balance equation to a form that allowed numerical solution providing the data concerning the cation exchange isotherm and the initial and boundary conditions are available.

FORTRAN programs were written for the numerical computation of the problem involved. The computation was done on a digital computer.

The model was verified by comparing the theoretically computed cation concentration profile with data from actual soil column experiments. The cation exchange of Mg→Ca was tested on Yolo fine sandy loam, Nibley clay loam and Haford Sandy loam columns. The exchange of Na→Ca was also tested on Yolo fine sandy loam. Satisfactory agreement between the column experiment values and the theoretically computed values was obtained.

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