Jukka Laine , Hannu Mannerkoski

Tensiometrin käyttö turvemaiden kosteusolojen kuvauksessa

Laine J., Mannerkoski H. Tensiometrin käyttö turvemaiden kosteusolojen kuvauksessa.

Tiivistelmä

The article presents results of tensiometer measurements in peat soils. Measurements have been taken both in the field and in the greenhouse. The plots in the field experiment represented different stages of drainage in ordinary sedge bog. Plot 5 was in a virgin state, plot 6 had been drained in 1967, and plot 3, in the 1930's. Each plot had one tensiometer at each of the three measuring depths. (5, 20 and 40 cm). In the field the depth of the ground water table was also measured using self-registering gauges. In the greenhouse experiment the water table in the soil samples was artifically regulated by raising it straight from the deepest level to the topmost level, and lowering it after every 2-3 days (see Fig. 3). The results are presented in figures 1-4. The soil water tension and hydrostatic pressure values obtained with tensiometers show a close correlation with those concerning the ground water table in case when the measuring unit has been near the water table or below it. Evapo-transpiration and rainfall caused a variation to the relationship between the water table and soil water tension at the depth of 5 cm, particularly when the water table was deep (30-40 cm) (Fig. 2). The effect of evapotranspiration can be seen also in the results of the greenhouse experiment (Fig. 4). In this experiment the effect of the rise of the water table was not as great as expected. The reason for this may be too short a time for levelling (2 days). The results show that tensiometers can be used also for measurements on the depth of the ground water table if it has a sufficiently assu-rate manometer and if the measuring unit is kept near or below the ground water table.

Vastaanotettu 31.10.2017 Julkaistu 1.1.1975

Katselukerrat 1413

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