EN
This work describes the fractional composition of acid formed humus based on physical-chemical and chemical properties in the Mollic Phaeozems Arenic and Mollic Gleysols Arenic. Sand and sandy loam with a decalcification feature dominates in terms of texture. Reactions of the studied soils range from strong light acid to alkaline. The organic O horizon and humic A horizon are very rich in C total. Alkaline character cations, mainly calcium and magnesium, dominated in the absorbing complex. The saturation degree of the sorption complex (BS) is very high in all profiles. With regard to the fractional composition, the Ia fraction represented a small part. Within the humus matter the I fraction dominates. The CHA-Ca (humic acids bonded with Ca) part is very high in both the organic O horizon and the humic A horizon. In turn, the content of non-hydrolyzed C total is minor in the organic O horizon compared with the humic A horizon. The high content of humic acids bonded with Ca (CHA-Ca) as well as strong humidity, the investigated soils favour stabilizing the soil organic matter despite the light texture.