DRAINAGE OF HISTOSOLS PUBLISHEDAdia GROZAV, Gheorghe ROGOBETE
Histosols form on parts of landscapes where there is concentration of run-on, retention of precipitation, or discharge of groundwater. Histosols cover approximately 275 million hectares plus 40 million hectares on humid coastal plains. In Romania, peat bogs are included in the class Histisols, with only one genetic type of soil – Histosol, that have in the first 100 cm of soil profile a T – histic horizon with at least 50 cm thick. Distribution of Histosols in Romania is in the high moor and in the low moor. The high moors are situated in 265 bogs, with 1351 hectarea, in the depressions of the mountains, like Sebeș, Semenic, Bucegi, Dorna, Borsec, Tușnad, Oaș. The low moors are in the bogs from Eriu, Crasna, Livada, Ciuc. The main process is the accumulation of organic materials under anaerobic conditions. Another difference with mineral soils is that peat soils show a certain rate of oxidation after drainage. Utilization of Histosols for cultivation is affected by several of their properties. In such cases the land needs some improvement methods, like a drainage system, liming material, chemical fertilizer. The consequences of an improved drainage are: shrinkage of the top layers; oxidation of organic matter; compression of the layers below the groundwater table; irreversible desiccation of the organic matter. A specific feature of Histosols is their generally low bulk density, which range from 0.19 to 0.22 g/cm 3 . Water content of Histosols are related to degree of decomposition, and ranged from 100% for undecomposed, near-surface sphagnum moss peat to less 80% for deeper, more decomposed peat. Field capacity at Histosols – Ciceu, ranged between 48.6 to 260.0 %. Saturated hydraulic conductivity ranges from 101 to 281 mm·h -1 . As far as the soil desiccates subsidence can be determined using the specific volume. Another approximation of subsidence can be found by applying the following formula: S=KDT 0.707 ; the subsidence will be 0.383m or 38.3cm. It will be clear that the prediction of subsidence is highly important to the planning of the drainage system. The optimum depth of the groundwater level of grassland in summer is in the temperate zone 50 to 70 cm below land level.
Histosols, peat, drainage, subsidence, oxidation