Acidity of KCl extracts from organic horizons of podzolic soils: Sources and possible equilibria

Samples from the organic horizons of taiga podzolic soils of the Komi Republic were studied, and the possible equilibria established in the soil-KCl solution system (c = 1 mol/l) at the determination of the exchangeable acidity by the Sokolov method were examined. It was shown that the exchangeable acidity was due to aluminum(III) ions in 6% of the samples with pH_KCl≤4 and due to the H⁺ ions formed during the dissociation of water-soluble organic acids in the other samples. A group of samples from the horizons in which Fe³⁺ ions could appreciably contribute to the soil acidity was discriminated.