A multiple ion uptake model

SUMMARY A model is developed which describes uptake of Ca, Mg, K, NO 3 , Cl, and SO 4 . The electrical neutrality of plant and soil are maintained through exchange of H or OH at the root‐soil interface, constant partial pressure of CO 2 and non‐exchangeable H reaction with the soil cation exchange complex. An important innovation in this model is the inclusion of electrical neutrality as a condition for plant, soil and soil solution. The uptake of cations is a function of both concentration of anions in solution and the suite of exchangeable cations. The model emphasizes an important role for CO 2 in soil chemistry and plant nutrition. Presently, the model is most useful for generating research hypotheses. Perhaps the most important hypothesis is that something about as complicated as the present model will be required to model multiple ion uptake and crop yields.