Hydrophysical Properties of the High-Ash Lowmoor Peat Soils

The water retention curve (WRC), density, botanical composition, and ash contents were determined for high-ash lowmoor peat soils (Rheic Sapric Histosols) developing on the floodplain of the Yakhroma River (Moscow oblast) from the herb-hypnum and hypnum peat enriched in carbonates, agromineral peat soils (Rheic Drainic Sapric Histosols (Mineralic)), and peat soils developed from woody peat underlain by herb, sedge, and woody peat layers (Rheic Sapric Histosols (Lignic)). The WRC was determined by capillarimetric method in the range of water pressure from 0 to 80-90 kPa. For the studied peat soils, the WRC represents a close to linear dependence of the water content on the water pressure in semilogarithmic scale. In contrast to mineral soils, a characteristic point of the air-entry pressure is virtually absent on the WRC of peat soils. The WRC of peat largely depended on their density: denser peat samples were characterized by a higher water content at the same water pressure, which attests to the increased water retention capacity. An increase in the degree of decomposition of peat and its ash content also leads to the rise in the water retention capacity, but the effect of these factors is considerably smaller than the effect of peat density.