THE EVOLUTION OF SOME TYPES OF SOIL UNDER THE INFLUENCE OF SURFACE EROSION
This paper presents the evolution of soil types under the influence of surface erosion. For this purpose, 4 soil profiles were executed on 2 types of soil (stagnic luvisol and stagnic preluvisol) near the Preajba Experimental Field, in the Gorj County.
In the stagnant luvisol, a comparative study was performed on a profile located on the plateau where the slope was between 2 and 5%, characterized by the following succession of Ao-Elw-ElBt-Bt1w-Bt2w horizons, the Ao horizon having a 24 cm development and the other one on an uneven side in the middle third with a slope between 10 and 15% having as a profile scheme Ao-Elw-Bt1w-Bt2w where the Ao horizon has a 15 cm thickness. The existence of slow geological (surface) erosion can be observed with this soil by analysing the development of the surface horizon.
At the second soil unit, at the stagnic preluvisol a soil profile was executed on the plateau with a slope between 2 and 5%, characterized by a profile of the Ao-Bt1w-Bt2w-Bt3w type, a 22 cm thickness of the surface horizon, and a profile on the same side in the middle third where the slope incline is between 10 and 15%, with approximately the same Ao-Bt1w-Bt2wC-C profile scheme, in this case the Ao horizon having a 14 cm thickness, which proves the surface erosion manifestation.Â Also, in the case of both soil types, by analysing the main physical and chemical properties, it has been shown that the loss of the soil layer from the surface, by washing year by year the fertile soil layer, gradually leads to the worsening of the chemical properties of the soil. Thus, the partial loss of the A horizon of the soils from slopes contributes to the increase of the apparent density on the profile, of the pH, of the waste coefficient, as well as the decrease of the total water capacity of the soil, of the field capacity, of the useful water reserves, of soil porosity, etc.