Tsutsuki, K., Suzuki, C., Kuwatsuka, S., Becker-Heidmann, P., Scharpenseel, H.-W. (1988): Investigation on the Stabilization of the Humus in Mollisols. Z. Pflanzenernaehr. Bodenk. 151 (2): 87–90.
Soil organic matter in Mollisols is often preserved for an extremely long period (e.g. 3000 years). We confirmed that the stable organic matter in Mollisols is the medium to coarse sized (0.2-2.0 µm) clay-humus complex with humic acid combined with calcium as the main organic constituent. The argillic horizon contained relatively large amounts of clay-humus complexes and had relatively high carbon contents, humic acid/fulvic acid ratios and degrees of humification of humic acid. Medium clay and coarse clay fractions preserved the organic carbon most efficiently. Highly humified humic acid could be detected even in the uppermost part of the Ah horizon and was probably stabilized in lower horizons by forming a complex with clay fractions.