T.S. Abdel Aal*, G.T.I. Abou EI-Hag** and Y. RA. Soliman( 2008). Contribution of Landsat Imagery to Identify the Physiographic Units and Soil Limitations for Agricultural Utilization at Southern-East Desert Outskirt of EI-Fayoum Depression, EgyptEgypt . j . soil .sci . 48 . no.3
Abstract: THIS STUDY was considered a trial to determine the contribution of Landsat Imagery for identifYing the main physiographic units and their soil limitations at South-East desert outskiIi of EI-Fayoum depression, Egypt, which represent the most urgent criteria help in planning the proper agricultural utilization projects. However, this technique is essential to conduct the preliminary soil studies in the wide desert areas for evaluating soil limitations in the current and potential conditions as well as suitable practices for favourable soil management and its sustainable cultivation on both the short and longterms. So, such area was selected as a model to be identified within the context of physiography, soil classification and land evaluation for irrigated agriculture. The obtained data show that the area under investigation includes both the continental alluvium of River Nile and desert deposits that were derived from foreign and local parent rocks, respectively. The physiographic units and their soil characteristics were identified based on the visual interpretation of Landsat data ETM7 (Enhanced Thematic Mapper 7) and applying the Landscape feature approaches. The main physiographic units could be categorized into seven units. i.e., piedmont, alluvial terraces (locally over blown sand), EI-Fayoum alluvial plain (locally terraced), EI-Fayoum alluvial fan, Nile alluvial depressed plain (River bed), Nile alluvial fiat plain and rock structures. The rock structures were delineated as dissected cuesta of summits and fronts or as rock outcrops. Thirty-seven mini pits were located and studied for setting up the legend characteristics of mapping units. The differences between these mapping units were represented by twelve soil profiles to be morphologically described and soil samples were selected for laboratory analyses. Studies of the fieldwork indicated that effective soil depth (45-75 em) was existed by bedrock in piedmont unit, while it was reached 150 em in soils of the other physiographic units. The majority of the studied soils are, in general, gravelly loose sand to sandy clay, besides the fine texture soils of El-Fayoum alluvial fan and the Nile alluvial plain. Most of the studied soils are suffering from salinity problems and noticeable decreases in soil organic matter. With exception of soils developed on either EI- Fayoum alluvial fan and plain or the Nile alluvial depressed and flat plain that dominated by smectites, the semi-quantitative determination of days indicated that kaolinite was the predominated one followed by smectites, illite; palygorskite, chlorite and vermiculite. Soil taxonomic units were identified according to the Key of Soil Taxonomy till the soil family 'level into:
i) Aridisols include a. Lithic calcigypsids, sandy skeletal, carbonitic, hyperthermic and Typic calcigypsids, loamy skeletal, carbonitic, hyperthermic in the piedmont unit and b. Typic Haplocalcids, fine loamy, mixed, hyperthermic and Typic calcigypsids, .sandy, mixed, hyperthermic in the alluvial terraces (locally over blown sand) unit.
ii) Vertisols include a. Typic Gypsitorrerts, clayey, smectitic,.hyperthermic in EI-Fayoum alluvial plain (locally terraced) unit; b. Typic Haplet9rrerts, fine clayey, smectitic, hyperthermic and Entic Haplotorrerts, clayey, smectitic, hyperthermic in EI-Fayoum alluvial fan unit; c. Halic Hapiotorrerts, very fine clayey, smectitic, hyperthermic in the Nile alluvial depressed plain (River bed) unit and d. Typic Haplotorrerts, fine clayey, smectitic, hyperthermic in the Nile
alluvial flat plain unit. iii) Entisols include a. Typic Torriorthents, sandy skeletal, mixed, hyperthermic and Typic Torripsamments. siliceous. hyperthermic in the alluvial terraces (locally over blown sand) unit and b. Typic Torriorthents, sandy, mixed, hyperthermic in EI-Fayoum alluvial plain (locally terraced) unit. According to the parametric system undertaken the current suitability of the studied soils could be categorized into four suitability classes [i.e., highly (S 1), moderately (S2), marginally (S3) and not suitable (NI)], besides eight subclasses, i.e., Nls1szs3n, S3sjsZs4n, S3sln. S3sj• S2n. S2sj• S2 and Sl, which were suffering from some soil properties (i.e., soil texture s" soil depth S2. CaC0353 and gypsum S4) and salinity/alkalinity (n) as soil limitations with different intensity degrees. So, further land improvement should be executed to achieve the potential suitability, i.e., highly, moderately and marginally suitable classes. In addition, the severity of soil limitations can be corrected by application of organic and inorganic soil amendments as well as drip irrigation system to sustain favourable soil moisture content for plants. These adaptations can be promising for rather higher output as the major land improvements are considered for the land qualities of drainage, salinity and sodicity, to maximize the current land suitability to be potential one after re-evaluating the physigraphic land considering them free of those limitations.
Keywords: (Southern-East desert outskirt of EI-Fayoum Depression.Physiographic-soil units, Soil taxa and soil evaluation for irrigated agriculture)
