The salt status of meadow-chestnut soils in the northern caspian region upon a rise in the ground-water level

摘要

It is found that the modern salt status of virgin meadow-chestnut soils of the solonetzic complex in the northern Caspian region is affected by the recent rise in the ground-water level. The latter began in the 1980s. At present, the ground-water depth is about 4.5 m in contrast to 6.5 m in the mid-1950s. The groundwater salinity has also increased from 0.6 to 3.2 g/l on the average. In the 1950s, the ground water under meadow-chestnut soils of the complex had the bicarbonate-calcium salinization; at present, it is replaced by the chloride-sulfate-sodium salinization typical of the ground water under virgin solonchakous solonetzes. The salt profile of the meadow-chestnut soils has become more complicated. The relative content of sodium chlorides and sulfates has increased. The total content of soluble salts in the 0- to 200-cm-thick layer has increased by three times. The contents of mobile Cl- and Na+ ions has increased by several tens of times and the content of less mobile SO42-, by five times. If the recent tendencies are preserved in the future, the salt status of the virgin meadow-chestnut soils should worsen under the impact of the capillary fringe of saline ground water.