TWO-DIMENSIONAL DISTRIBUTION OF SALINITY IN IRRIGATED SOILS NEAR THE IRRIGATION CHANNEL AT THE PLOT "CHERVLENOE" OF THE SVETLOYAR IRRIGATION SYSTEM

The current state of irrigated soils’ salinity at the key plot located along the buried irrigation channel within the irrigated plot Chervlenoye of the Svetloyar Irrigation System (Volgograd Region) was studied. In the 1990-s a strong sec-ondary soil salinization was detected during the aerial survey. Its boundaries were clearly observed on the image. After the irrigation had been ceased, a par-tial soluble salts leaching from the soil took place at the key plot as a result of precipitation and decrease of the groundwater table. Basing on the field data obtained in 2017 a model of two-dimensional distribution (depth, distance from the irrigation channel) of the ion activity (Ca2+, Cl–, Na+) was created. It was found that sulfate-chloride-sodium type of salinization prevails which is typical for natural soils at the studied territory. However, the traces of secondary sali-nization expressed by the presence of calcium chloride in soil solution are pre-served in a number of soil horizons. According to the depth of the upper saline horizon, the soils belong to solonchakous type, the distribution of salts is medi-ocre-accumulative, maximum of salts is located at a depth of 100–150 cm.