Description of soil chemistry during transient solute transport

Leaching studies were conducted in six instrumented field plots to establish the validity of a soil chemistry‐solute transport model. The model was designed to predict the transport and solution concentrations of Ca 2+ , Mg 2+ , Na + , K + , HCO 3 − , CO 3 2− , SO 4 2− , and Cl − in a soil containing CaCO 3 (lime) and CaSO 4 ·2H 2 O (gypsum). The model includes description of the precipitation and dissolution of both lime and gypsum and considers cation exchange. Evaluations were made of the sensitivity and accuracy of model simulations under transient and steady state flow regimes and in cropped and noncropped situations. The leaching plots were instrumented with porous ceramic suction samplers, tensiometers, and neutron probe access tubes. Five different quality waters and three types of water management were used. The soil solution was sampled following each irrigation and analyzed for the cations and anions of interest. Comparisons of measured and predicted data showed the model to be reliable as a simulation tool to predict electrical conductivity under cropped conditions but unreliable in uncropped situations.