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Abstract The study area occupies a portion of the North western coastal belt of the Mediterranean sea which is considered among the accessible areas attaining the most promising lands for agricultural expansion beyond the Nile valley and Delta. It extends from Alexandria on the east to Ras El-Dabba on the west, between latitudes 30° 40 and 31° 10 N and longitudes 28° 20 and 29° 50 E. The physiographic features of the area are presented with particular emphasis to the major features of the environments pertaining to the land use, namely; climate, geology, geomorphology, ground water conditions and vegetation. The aim of the current work is to demonstrate the applicability of qualitative and quantitative systems for assessing land capability on basis of most soil properties relevant to pedogenetic classification. To fulfil the aim of the study, 29 soil profiles stretching along the study area are chosen to cover the major soil mapping units encountered in the area in regard to geomorphologic aspects. These profiles are morphologically described and 85 soil samples were collected to represent the morphological variations within the entire depths of profiles. These samples were evaluated for their relevant physical, chemical and mineralogical properties. Besides, field infiltration tests were conducted adjacent to the most representative soil profiles. The obtained data reveal that though the studied soils have interrelated origin, yet their profiles display a wide range of variability in their properties, depending on locality, lithology, landforms and depositional environments. The most prominent feature is that particle size distribution and textural classes vary considerably from one profile to another and even in the subsequent layers of some profiles. Consequently, the soil mapping units are distinguished on basis of gemorphology (landforms) and textural variations. Briefly, the obtained results are summarized as follows. 1- Texture varies widely from sand to clay. The soils are non saline to extremely saline with an apparent dominance of Na+ and C1- in the soil extract. Soil reaction is neutral to alkaline. Cation exchange capacity varies widely from about 3 to 23 me/l00g with a dominance of Ca on the exchange complex. Organic matter content is very low, not exceeding 1.4%. The macronutrients(NPK) levels are seemingly low, indicating inadequacy of N and,to some extent,P while K level lies within the sufficient range. 2- Rating of morphological properties was figured out using the relative horizon distinctness and horizon index. Modifications of the morphological rating systems was provided through the inclusion of missing data concerning CaC03 and salinity which have significant importance in the studied soils. Their results indicate apparent discontinuity and stratification of profile layers as shown by the variations in RHO and horizon indexes. 3- CaC03 content ranges widely from 17.77 to 94.48% with apparent increase of carbonate in the finer soil fractions except for the oolitic dunes. 4- Amorphous inorganic materials content ranges from 1.1 to 4.6, 0.05 to 0.5, and 0.4 to 4.6%for 5i02, A1203 and Fe203, respectively. The vertical distribution of these components does not follow any specific pattern pertaining to lithology, locality or landform. The regional distribution indicates an increase of silica due west in contrast to alumina while both components increases from the sea shore southwards. Amorphous iron have a common pattern characterized by a pronounced increase with the fineness of textural classes and also in the deepest layers of profiles. 5. Chemically extractable micronutrients vary widely from 0.36 to 2.31, 0.05 to 1.82,0.5 to 3.9, 0.5 to 14.8 and 0.05 to 9.04 ppm for hws-8, EOTA-extractable Cu, Zn, Mn and Fe, respectively. These levels indicate that the coarser the texture the lower is hws-B and vice versa. Conversely, higher EOTA-extractable Cu and Zn is associated with finer texture. A regional distribution of these elements indicates that the weighted means of hws-B and EDTA-extractable Cu tend to decrease westwards to El-Hammam then become almost constant while they increase southwards from the sea shore inland. For Zn and Mn, the maximum weighted means correspond to the soils of Burg El-Arab and decrease progressively due East and West while weighted mean of Fe displays a steady decrease on passing from Maryut soils westwards. The similarity of weighted means in some profiles representing different geomorphic units may indicate an interrelated origin of the studied soils. The relationship between micronutrients and soil variables was also evaluated through statistical analysis. 6- Mineralogy of the sand fraction reveals that the light fraction is generally dominated by quartz with less pronounced amounts of feldspars (orthoclase, plagioclase and microcline). The heavy residue is composed essentially of opaques followed by pyroboles, epidote, ubibuitus and parametamorphic minerals in different frequencies. The vertical distribution of these minerals verifies the multi-depositional regime of the non uniform parent material already established through rating of morphological properties. 7~ Mineralogy of the clay fraction shows that palygorskite dominates the mineralogical composition of clays irrespective of location, mode of formation or depositional environments. The relation of clay minerals to lithology, landform and depositional environments were also correlated with soil origin and genesis. 8- Moisture characteristics coincide very well with textural variations among soil profiles and layers. 9- Infiltration studies of the representative profiles indicate a rapid to moderately slow infiltration class depending on textural variations and succession of layers throughout profile depth. The effect of soil variables on infiltration parameters was evaluated statistically. 10- Soil classification was carried out following the most recent American system ”Soil Taxonomy, 1975” down to the family level. Briefly, the soils are placed as Typic and Lithic Torripsamments. Typic and Lithic Torriorthents, Typic Calciorthids and Typic Salorthids. On basis of particle size class within the profile control section,mineralogy, soil moisture and temperature regimes, soils belonging to the former taxonomic units are differentiated into five families. 11- Based on the foregoing soil characteristics and recognized agricultural limitations, qualitative land capability classification was performed using the USDA system (1973), Parson’s system (1962) and FAD framework of land suitability classification (1976). According to these systems thesoils are placed under classes III to VII, II to V and S1 ’ S2 ’ S3 ,N1 and N2 ’ respectively. Quantitative land capability classification is also worked out following both the modified Storie index (1933) and Sys and , Verheye system (1978). Accordin9 to these systems the soils of the study area are grouped into classes C, D and E and 51’ 52’ 53’ N1 and N2, respectively. Each of these systems of land capability classification is critically criticised and its applicability on the study area is discussed. Moreover, modifications for the quantitative systems to suit the highly clacareous conditions of the arid and semi-arid lands are suggested. |