This work concerns the constitution of a soil database of the Sahara areas in which 628 standard profiles are compiled. \nThe 2428 described horizons and the 1990 analysis revealed that these studies are not always undertaken according to recognized steps and standards. Thus, it proves that pedological information is not always indicated. Indeed, only approximately 20 % of the descriptive or analytic variables are indicated with more than 70 %. This result means that there would be a loss of pedological information. The confidence tests between some pedological variables pairwise revealed that their agreement varies between 26 % and 97 % according to the pair considered. This result alone shows the absence of a rigorous control of the data at the time of the realization of the soil survey. \n The statistical analysis of five pedological parameters (clay, carbonate calcium, gypsum, organic matter and EC) in three categories of horizons (H1, H2 and Hp), on the Sahara (data base), showed that the saharian regions are not or far from clayey (more than 50 % of the horizons), slightly limestone in their majority (39 % of the horizons contain less than 10 % of limestone), not gypseous (more than 50 % of the studied horizons contain less than 3 % of gypsum) and not very organic (90 %). On the other hand, they are, for the majority, very strongly salted with a preference for the surface horizon in 50 % of the case. \nLastly, calculations showed that each one of these parameters are variable somehow strongly in the space and in the profile. \n The third aspect of this work concerns the search for possible relationship between the studied parameters. \nThe principal results are: \n- Generally, when the CaCO3 rate increases in the ground, the clay rates have tendency to decrease. However, one can meet grounds which are clayey but not very calcareous, or on the contrary very calcareous and not very clayey. \n- The grounds calcarious soils are generally not very gypseous. In the same way the gypseous soils are not very calcareous.\n- The relation between the gypsum and clay rates are negative and statistically highly significant.\n- The increase in the gypsum rate is accompanied by a reduction of the electrical conductivity.\n- The increase in the carbonate calcium rates beyond 30 % is accompanied by a reduction of the EC. \n\nKey words: The Sahara, database, clay, carbonate calcium, gypsum, OM, EC, correlations.
Author(s): Ismaiel Berkal, Didier Michot, Tahar Idder, Abdelhak Idder, Kaddour Djili