Water Retention and Saturation Degree of peat soil in Sebangau Catchment Area

Water is one of the important factors role in forming, cultivated, and utilization management and sustainability of peat soil. The aim of this study was to obtain the characteristic of water retention and porosity of peat soil. The study was conducted in the Natural Laboratory of Peat Forest, located in the Sabangau catchments areas, Central Kalimantan Province. Peat sampling was taken from three-peat thickness categories, i.e. shallow peat, medium peat, and deep peat, at depth peat layer of 0-50 cm and 50-100 cm layer. The result of the study has shown that the relation of bulk and particle density with porosity was a weak tendency, although the porosity trend to decrease while increasing the bulk and particle density, however that has a low of regression coefficient (R). The volumetric moisture contents of the peat matrix have the same trend for three-peat thickness categories. Shallow peat moisture levels always appear to be higher than medium peat and deep peat, and this occurs both for the top surface (0-50 cm) and for subsurface (50-100 cm) peat layer. This may be related to the solubility of soil mineral materials in the peat matrix, which is supported by the presence of a peat layer that coincides with the mineral layer in the ground. While there is a driving force to release water from the peat matrix equal to a pressure of 15 atm, less than 20 % of the volume of the peat matrix still filled water, and when that is equal to a pressure of nearly 0 atm (in a flooded field) or saturated, a maximum of 86% of the volume of the peat matrix is filled by water. The saturated degree of shallow peat at the level pF ³ 1 (pF 1 - pF 4.2) always high compared to the medium peat and deep peat, both at the surface layer (0-50 cm) and subsurface layer (50-100 cm), while at pF 0, is always lower than that of medium peat and deep peat. For all of the peat thickness categories, a saturated degree at the surface layer is not significantly different from the subsurface layer