Calcium Carbonate Equilibria in Soils

A thorough understanding of calcium carbonate equilibria is essential to the development of computer models capable of predicting the effect of irrigation management on water quality degradation in irrigated areas.

The objectives of this research were: 1) to develop a model capable of describing calcium carbonate equilibria in soil solutions, and 2) to test the model against data for calcareous soils equilibrated with waters of various compositions.

A chemical model developed previously and capable of describing calcium carbonate equilibria in aqueous systems open to the atmosphere was applied to soil systems. Published data for large lysimeters irrigated repeatedly with waters characteristic of Western United States rivers were used to verify the model.

The model is chemically sound and compares favorably with a more empirical computer model developed by the U.S. Salinity Laboratory which adequately predicts water quality changes as a function of irrigation management. Lacking further refinement of the models to include additional soil solid phases, the Salinity Laboratory model is preferable to the model based on pure calcite as the dominant CaCO ₃  form in soils.

Project 3109-146