The highest rates of acidity generation occurred within the first 20 days of incubation.

Soil pH decreased rapidly by ~ 2–3 units, while titratable actual acidity increased.

RIS species decreased over time.

The reactive pool of Fe (III) minerals (e.g. schwertmannite) increased.

Sites located at lower elevations contained higher initial RIS and generated more acidity.

The magnitude of acidity generation was less than the theoretical calculations.