Effects of saline conditions on the soil porosity in the Cheliff valley, Algeria

الملخص EN

Porosity variations of the saline and sodic clay soil have been studied by several approach methods (mercury porosity, final infiltration, water retention and microscopic observation).

The main results showed that the stress saline conditions permitted to increase the total poral volume (VT) of aggregations.

Indeed, a saline constraint of the exchange sodium percentage (ESP) of 52.5% caused an increase in the total poral volume of 63.4 %.

The distribution curves of pore diameter resulted in the existence of three different poral volumes of VA, VB, VC, corresponding to the structural, lacunar and clay pores, respectively.

The results showed also that both the structural porosity and lacunar porosity were linearly related to the ESP.

This was not the case for the clay porosity, which decreased with increasing the soil salinity and sodicity.

The results of the influence of the ESP on the evolution of the poral volumes showed that below an ESP level of 11%, the poral volume decreased in the order of VC > VA > VB.

However, above this ESP level, the tendency reverses resulting in an order of VA>VB> VC and a stabilization in the final infiltration level of the soils corresponded to a complete extension of the sedimentary crust.

The micro morphological observation of the thin section makes easier the interpretation of the poral space, provides first the essential information concerning the micro structural organization at the aggregate level with its regular assembly, and then develops the mechanisms of disintegration until the reorganization to the level of the massive aggregation with formations of micro horizons.

The main feature is that the presence of a structural poral space under saline conditions does not necessarily make sure a more elevated level of infiltrability because it can function very well only by the textural pores or by the cracks of climatic origin.

The clay phase is abundant; its poral volume decreases in regard to the other pore volumes; it is due to the role of the sodium in the clay particle division, which causes an increase in the number of the contact surface that is responsible of fine particle assemblies with the skeleton.