WATERLOGGING OF GROUNDWATER ORIGIN AND CRITICAL MINERALIZATION AS PROCESSES OF SOIL DEGRADATION RESULTING FROM NATURAL SPECIFIC CONDITION, WITHIN DOLJ COUNTY, ROMANIA,

ABSTRACT

The soil is one of the most complex natural systems of Earth. By its features, the soil reflects the impact of clime, flora, fauna, human activity and topography on bedrock from which the soil was formed during various periods of time, being considered an indicator of environment evolution. The soil degradation means the quantitative and qualitative diminishing of the current potential yielding capacity of soil that contributes to the production of goods and services as a result of some unfavorable evolution, by diverse natural processes or generated by improper human activity on environment, in general and on soil in particular. Salting is a natural process of soil degradation which means the soil enrichment in salts that are brought by water in solution or along with clay material as suspension. Their presence into the soil is closely related to shallow and salty groundwater in certain areas which, by capillary ascension get up into the soil up to the surface and by water losing through evaporation, the salts are concentrated into the shallow layer of soil as stains, veins, small tubes or pseudomicelles The soil degradation through these processes determines the worsening of physical and chemical features of these soils and, consequently, the diminishing of their natural fertility and yielding capacity. Specific natural conditions for this phenomenon are encountered within the Southern zone of Dolj County where there were identified as soil units formed in waterlogging conditions associated with a critical mineralization, the saline gleisoil and saline solonetz. The groundwater excess and critical mineralisation have determined the formation of gleisation process to the soil within researched area (G horizon) salinisation (sc horizon) and alkalisation (na horizon) that determine unfavorable physical, chemical and biological features for plant growth and development. As a result of high sodium content there take place a dispersion of soil colloids which destroys the soil structure. This fact determines an extremely reduced air and water permeability and, consequently, a very high compaction. The high content of soluble salts of these soils increases the osmotic pressure of soil solution, over the limits of water accessibility for plants which determines a water deficit for plants. The indicators of soluble salts presence in the conditions of a semiarid climate, with the water table at shallow depth and variable level are emphasized by the alkaline reaction (pH over 8) and a basses saturation degree within eutrophic domain (V%>100) with both soil units.

Keywords: soil, degradation, critical depth, critical mineralisation, natural fertility, yielding capacity