Siwa Oasis is a closed depression situated in the north western portion of the Western Desert of Egypt
between Longitudes 25º 16' and 26º 12' E, and Latitudes 29º 06' and 29º 24' N.
Three soil profiles were selected to represent the main geomorphic units and their associated soil groups
in the studied area.
Ghazallat soils are characterized mainly by sand and sandy loam textures, as well as sandy clay loam
in the deeper layers.
The chemical analyses of soil solution indicate that the cultivated soil samples show slightly saline to
moderately saline nature, whereas the soils under reclamation and the barren ones are strongly saline. In
general the organic matter contents are low, while CaCo3 content increases from the deeper samples to the
higher ones. As for the soil reaction of Ghazallat area, it is clear that these soils are ranging from mildly
to moderately alkaline. It is noticed that Na+ cation > Mg++, Ca++ and Mg++. The predominance of Na+ and
Mg++ is a good reflection of the involvement of marine origin of the soils. On the other hand, the anionic
distribution has the following descending order Cl- anion > SO4
-- > HCO3
-, where CO3
-is almost negligible.
The distribution of the fertility elements are of low to moderate levels.
The bulk samples analysis indicates that quartz, calcite, feldspars (albite) minerals are the main
dominant mineral associations in all soil profiles of Ghazallat region. Dolomite and anhydrite as well as
gypsum presented in some depths of soil profiles. Illite and kaolinite represent the identified clay minerals
in the studied soil samples.
The radiometric studies show that all of the studied soils in the area are not related to the uraniferous
soils (uranium content not exceeding 6ppm).