Oasis lands in Egypt are commonly described as salty soils; therefore, waterlogging and higher soil salinity are major obstacles to sustainable agricultural development. This study aims to map and assess soil salinization at El-Farafra Oasis in the Egypt Western Desert based on salinity indices, Imaging Spectroscopy (IS), and statistical techniques. The regression model was developed to test the relationship between the electrical conductivity (EC_e) of 70 surface soil samples and seven salinity indices (SI 1, SI 2, SI 5, SI 6, SI 7, SI 8, and SI 9) to produce soil salinity maps depending on Landsat-8 (OLI) images. The investigations of soil salinization and salinity indices were validated in a studied area based on 30 soil samples; the obtained results represented that all salinity indices have shown satisfactory correlations between EC_e values for each soil sample site and salinity indices, except for the SI 5 index that present non-significant correlations with R² value of 0.2688. The SI 8 index shows a higher negative significant correlation with EC_e and an R² value of 0.6356. There is a significant positive correlation at the (p < 0.01) level between SI 9 and EC_e (r = 0.514), a non-significant correlation at the (p < 0.05) level between soil EC_e and SI 1 index (r = 0.495), and the best-verified salinity index was for SI 7 that has a low estimated RMSE error of 8.58. Finally, the highest standard error (R²) was represented as EC_e (dS m⁻¹) with an R² of 0.881, and the lowest one was SI 9 with an R² of 0.428, according to Tukey’s test analysis. Therefore, observing and investigating soil salinity are essential requirements for appropriate natural resource management plans in the future.

The study area capability evaluation was carried out using land mapping units characteristics compared to capability class critical limits. The study area soils were classified and identified into two soil orders; Entisols and Aridisols, characterized by eight great groups ▫“Vertic Torriorthents, ▫Typic Calciorthids, Typic Paleorthens, Typic Torrifluvents, ▫Typic Torriorthens, ▫Typic Torripsaments, Lithic Calcic Gypsiorthids and Lithic Torripsaments”. Soils were classified into four classes of land capability C3, C4, C5 and C6; Decantation Basin, Delta, Alluvial Fans and Dry Wadi were ranged between C3 which have good capabilities and can be manageable with minor impediments, and C4 (moderate capability) with moderate to low restrictions that limit the crops sets and soil particular maintenance and conservation techniques are necessary. While, Terraced Hills, Pediplains, Footslopes, Wet Sabkhas and some areas of Coastal Plain belonged between C5 with moderately severe limitations that limit the types of crops that can be grown with specific conservation, and C6 (low capability) with very severe limitations that reduce their usage in agricultural practices. These soils are suitable for growing forage crops, and agroforestry systems since they have low to marginal productivity. As a result, South Sinai soils have some sustainable soils that might potentially play a significant role in aiding decision-makers in modifying and creating sustainable programs and expanding the highly capable areas.

Soil minerals represent an important component of its system, andstudy of their role in soil fertility is essential for better soil managementand consequently high productivity. The aim of this research is to study the influenceof soil minerals on some soil fertility attributes such as clay percentage, OM and CEC. Physical and chemical properties of clay minerals affect soil fertility by controlling nutrient availability and supplies, through the stabilization and sequestration of soil organic matter. Clay minerals also affect soil physical properties through microaggregate formation and controlling soil microbial population and activity. The soils of the study area had a coarse texture with low water retention and high permeability. The clay content is very low. Quartz grains are one of the most common detritus minerals present in different percentages. It was derived from granite and sandstone as parent materials in the study area. Most quartz contains extremely low concentrations of plant nutrient elements other than Si. Although quartz is highly resistant to weathering, silica is slightly soluble at the common pH values of soils.Feldspars are alkali aluminosilicates and are, by far, the most abundant igneous rock forming minerals. Calcite is a calcium carbonate mineral, which was formed in the study area form the breakdown of the carbonate rocks e.g. limestone and dolomite. The low soil-CEC and low organic matter are the main fertility constraints of these soils. Therefore, organic matter application is recommended to improve CEC, carbon content, and nutrient availability.

The study area was situated in South East Egypt, which includes soils of different parent rocks and different parent materials. These soils were either regionally derived from sandstone parent rock or continentally from basement complex parent rocks forming River Nile alluvium. Remote sensed data were manipulated from the satellite TM8 2020 for delineating the physiographic units on the base of reflected spectral signatures of different landscape elements, which cover 386,171.04 hectares. Two groups of physiographic units were identified as having different genesis. One of these groups includes dissected rock land of sandstone, pediplain of residuum, bajada and wadis of alluvium. Another group includes River Nile alluvium as levees, point bares, bow bars and alluvial plain. Soil taxa of those physiographic units were categorized as three soil orders to the level of soil family. These soil taxonomic units are: Aridisols includinga) Lithic Calcigypsids, coarse loamy, mixed, hyperthermic in pediplainwithinclusion of Lithic Calcigypsids, sandy, mixed, hyperthermic; andb) Typic Haplogypsids, coarse loamy, mixed, hyperthermic in bajada. Vertisols include Typic Haplotorrerts, fine, hyperthermic in River Nile alluvial plain. Entisols including: a) Typic Torrifluvents, fine loamy, mixed (calcareous), hyperthermicin wadis with inclusion of Typic Torrifluvents, fine loamy over sandy, mixed (calcareous), hyperthermic.; b) Typic Torriorthents, fine loamy, mixed, hyperthermic occurred in levees.; c) Typic Torriorthents, fine loamy over sandy, mixed, hyperthermicin point bars; and d) Typic Torriorthents, coarse loamy, mixed, hyperthermic in bow bar.