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It is well known, that soil particle surface properties like cation exchange capacity, surface area, and charge density affect ion-exchange reactions in the root zone. However, the exchange processes at the root surface itself also depend on these properties: cation exchange capacity, surface area, which will be determined in this paper for the roots of young wheat, barley, rye, triticale, and maize plants. Undisturbed samples from a Haplic Luvisol developed from loess were taken at 5–10 cm depth from an “normally compacted” core part of the crop field (Ref.) (bulk density 1.29 ± 0.06 Mg m⁻³) and from a “compacted” (C) (bulk density 1.61 ± 0.05 Mg m⁻³) part in the headland. Plants were grown in these soil cores for 11 days in a growth chamber. The negative surface charge of the roots and apparent surface dissociation constants were determined based on potentiometric titration in pH between 3 and 10. The surface …