Calculating Cation Exchange in a Salt Transport Model

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Abstract
A cation exchange subroutine that can be expanded to include any number of cations was developed and interfaced with a water flow‐salt transport model that also contained a lime and gypsum precipitation‐dissolution chemistry subroutine. The exchange subroutine was required by the complete model to satisfactorily predict EC, SAR, and specific ion concentration changes with time and depth for a gypsiferous and a non‐gypsiferous soil irrigated with waters containing three different CaSO4 concentrations at two leaching fractions. In his sudy, exchangeable Ca, Mg, Na, and K were considered. Exchangeable K was included for use with high exchangeable and soluble K soils and high K irrigation waters. The additional cation exchange coefficient values needed for K exchange and a method for their calculation is given.
Funding Information
  • Office of Water Resources Research
  • USDI (JEA-113-1)