The study was carried out to show the effect of the clay characteristics:
specific surface area (Ss), cation exchange capacity (CEC), and the assemblage
of clay particles on the soil water content. The effect of hydric stress history
(wetting and
drying cycles) on the water content of soil was also investigated.
Soil samples comprising topsoil horizons and subsoil horizons, with a clay
content > 30% were collected in several regions of France and Syria (2009 -
2012) in cooperation with the National Center for Scientific Research and the
University of Orléans in France to study the effect of physical characteristics on
the fertility status of the soil. The water retention properties were studied from
(0.01) bar to (15) bar water potential using small clods collected in winter when
swelling is at a maximum and water content close to field capacity. The clay
content, the bulk density of horizon and clods, the cation exchange capacity and
the specific surface area were measured. The X-ray diffraction (XRD) was used
for identification of the main mineralogical phase, and to study the relationship
between the clay mineralogy and the water retention. Results showed that the
variation of the soil water content was explained by the differences of clay
content and the clay fabric (assemblage of clay particles). The results also
showed that wetting and drying cycles were the most important and critical
factor for soil water retention properties relative to the other evaluated factors.