You find that the CEC of a sandy loam soil at pH 5.0 is 8 cmolc/kg and at pH 8.2 it is 14 cmolc/kg. What is the most likely reason for this difference?
A) replacement of trivalent Al3+ ions with divalent Ca2+ ions at high pH.
B) increase in the pH-dependent charges on 2:1 type silicate clays
C) ionization of carboxyl and phenolic groups to release H+ ions
D) removal of Al atoms from tetrahedral layers at low pH.
E) removal of Al3+ ions from the exchange complex at higher pH.
C
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