Summary
Soil samples obtained from genetic horizons of two upland soils and an acid sulphate sub-soil of Sierra Leone West Africa, and crushed to pass a 2 mm sieve were equilibrated with 0.01M CaCl2. Mn+2 activity was estimated from measured total Mn, accounting where necessary for the MnSO4 0 complex specie.
Mn+2 activity was much lower than those predicted for equilibrium with a number of Mn minerals. It seems probable that known simple silicates, sulphates, phosphates, oxides and hydroxides of Mn are too soluble to persist in the fine earth fraction of these highly weathered soils of low pH. Observed Mn+2 activity may be governed by exchangeable and/or other forms not evaluated here.
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