| Sumario: | The CEC of the soils and subsoils from eight sites derived from more or less recent volcanic ash from the Irazii massive in Costa Rica was studied The CEC deter-minations were carried out on field moist and an dried samples and on samples after organic matter destruction using Na, NH₁, Ca, Mg and Ba as saturating cations and pHs of 7 to 8.2.
Very low CEC was observed for the very recent surface soils which increased for subsoils. The more developed soils showed the contrary tendency Air drying reduced CEC when determined with Na, but it was little affected, when divalent cations were used
Organic matter destruction has a variable effect on the CEC of the studied samples probably due to their variable mineralogy.
The CEC valnes for monovalent cations were higher than for divalents There was a good corelation within the monovalent and divalent groups, but not between specific elements.
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