SOIL PHYSICAL QUALITY AS QUANTIFIED BY S INDEX AND HIDROPHYSICAL INDICES OF SOME SOILS FROM ARGEŞ HYDROGRAPHIC BASIN PUBLISHEDOlga Petruta VIZITIU, Irina CALCIU, Ioana PĂNOIU, Catalin SIMOTA
This paper presents the soil water retention curves determined on two soil types from hydrographic basin of Arges River: P1 - Eutricambisol tipic, P2 - Vertisol stagni-pellic. Undisturbed soil cylinders were sampled on the genetic horizon depths characteristic for each soil type. The soil water retention curves were measured in the laboratory using standard equipment for retention measurements supplied by the Dutch Eijkelkamp company. The principle of the method is based on the determination of the soil water content corresponding to a certain level of water suction applied. By applying the Solver Microsoft Office Excel program the measured values of the water content from soil water retention curves were used to estimate the parameters of the van Genuchten equation which were later used to estimate the soil water retention curves and the main hidrophysical indices: field capacity (FC), wilting point (WP) and plant available water (PAW). The obtained results have illustrated the evident similitude between the estimated soil water retention curves from the van Genuchten equation and the measured soil water retention curves in the laboratory. Then the S index for agricultural soil physical quality was estimated using also the parameters of the van Genuchten equation. The S index is defined, in terms of the van Genuchten parameters, as the slope of the water retention curve in its inflection point. The estimated values of S have showed that the soil with more equilibrate medium texture (soil profile P1) has higher values of the S index for estimation of the soil physical quality as compared with the clayey heavy textured soil (soil profile P2). Consequently, the soil Eutricambisol tipic (P1) has a higher soil physical quality then the soil Vertisol stagni-pellic (P2). The good physical condition of the medium textured soil (soil profile P1) as quantified by S index is associated with an increase of the water storage capacity of the investigated soils. Moreover, the shape of the soil water retention curves of the soil Vertisol stagni-pellic (P2) illustrates that this soil presents the degradation processes of its physical condition.
soil water retention curve, soil physical quality, S index, van Genuchten equation, hidrophysical indices