In order to determine the direction of moorshy soil organic substance transformation, especially its fraction composition, under different humidity conditions laboratory experiment was carried out using a Column Device for investigation the soil with irrigation (PO no. 54427). Soil material was taken from accumulation horizon of mineral-moorshy soil from the 0-10 cm layer, placed in columns and irrigated after appropriate preparation using following water doses: 0 – without irrigation, I – to fill the capillary water capacity, II – 615 ml, III – 1042 ml, IV – 1657 ml. The fractions of humus, reaction, sorption properties and total content of carbon and nitrogen were determined in the soil material with methods commonly used in soil science. The results indicate that along with the increase of water dose increase the amount of eluted total carbon from the soil material. Quantity changes of total carbon are accompanied by qualitative and quantitative changes of particular determined humus.