Question

Explain why humus have higher cation exchange capacity (CEC= 200 to 400 cmol+/kg) than montmorillonite (CEC = 80 to 100 cmol+/kg).

Answer 1

Humus is a colloidal substance enriched in organic matter. These organic colloids have relatively large quantities of negative charges that are higher compared to montmorillonite represented by silicon-enriched mineral. As humus is more negatively charged, it can bind a higher number of cations resulting in higher cation exchange capacity than montmorillonite.