الفهرس 
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Abstract
Wadi Qena is one of the largest dry valleys in the eastern desert of Egypt for the agricultural expansion. It is located east of Qena city and constitutes the western part of eastern desert plateau. The investigated area is located in the middle part of wadi Qena, eastern desert, Egypt. It is limited between longitudes 32° 44ꞌ to 32° 49ꞌ E and latitudes 26° 30ꞌ to 26° 36ꞌ N. It lies the north of the proposed Golden triangle, about 135 km from Sohag city and about 83 km from Safaga city. It extends for 60 km starting from the intersection of Sohag-Qena-Safaga highways at the middle part of the wadi Qena. The total study area is about 62.171 km2 representing nearly 6217.1 hectares (about 14796.7 feddans). The study area is considered one of the most favorable areas for agricultural expansion.
The current study aims to:
1- Investigate the soil properties of the middle part of wadi Qena, eastern desert, Egypt,
2- Classify the soils of this area according to Soil taxonomy (Soil Survey Staff, 2014),
3- Evaluate its capability using the the applied system of land evaluation (ASLE) (Ismail and Morsi, 2001) and the modified Storie index (O’Geen et al., 2008),
4- Assess its suitability for growing crops under irrigated agriculture using the applied system of land evaluation (ASLE) and the rating classes suggested by Sys et al. (1991 and 1993).
To fulfill the objectives of the study, forty-nine soil profiles were selected to represent and cover the area under study. The points of the soil profiles of the investigated area were located using the Global Position System (GPS). All soil profiles were morphologically described according to the standard procedure and terminology as reported by FAO (2006) and Schoenberger et al. (2012) and 133 soil samples were collected from the different layers of all investigated soil profiles according to vertical morphological variations. The soil samples were subjected to different laboratory analysis. Land productivity use is controlled by the soil physical and chemical characteristics of the investigated soil profiles and their spatial distribution. Spatial data of soil profile properties were presented as individual maps by GIS (e.g. texture, bulk density, salinity, soil pH, calcium carbonate contents, gypsum, CEC and ESP as well as available N, P and K. According to the US Soil Taxonomy (Soil Survey Staff, 2014), the soils of the study area were classified down to the soil family level. All maps of soil properties, land capability, land suitability were produced using Agric. GIS 10.8 software (ESRI, 2019).
The results obtained from the current study could be summarized in the following:
1 – Soil Physical and Chemical Properties
The soils under investigation show wide variations in the physical and chemical properties that can be abstracted in the following:
• The soil texture is mostly coarse, mainly sand, loamy sand and sandy loam. In addation, the gravel percentage ranged between non and 59.77 %.
• The bulk density and porosity of these soils ranged from 1.53 to 1.86 Mg/m3, and 28.34 to 40.48%, respectively. The low values of the total porosity of this coarse-textured soils is associated with their high values of bulk density. In most cases the distribution pattern of the total porosity values of the study area increases with depth because the gravel content, coarse texture and calcium carbonate content decrease down word. In other words, this may be related to a high content of the sand fraction and to their lower contents of silt, clay and organic matter.
• The hydraulic conductivity varies from 3.19 to 37.10 cm/h, due to the effects of the variability of soil sedimentation and hydrologic processes.
• The saturation percentage (SP) varied from 21.2 to 38.2%. Moreover, the field capacity, wilting point and available water values of the studied soil samples range between 10.93 to 25.47 v/v%, 5.38 to 11.58 v/v% and 5.54 to 16.02 v/v%, respectively. The highest values of field capacity, wilting point and available water were found in silt loam and loam textures, whereas the lowest ones were found in sand, loamy sand and sandy loam textures.
• The soil pH considerably varies between 7.70 and 8.81 indicating moderately alkaline to strongly alkaline soil pH showing no specific trend with depth.
• The soil salinity in these soils varies from non-saline to very highly saline, where the electrical conductivity (ECe) differs from 1.50 to 154.20 dS/m. About 2.04% of the total soil samples are non-saline (ECe < 2 dS/m), 6.12% are very slightly saline (ECe 2 to < 4 dS/m) 6.12% are slightly saline (ECe 4 to < 8 dS/m) 26.53% are moderately saline (ECe 8 to < 16 dS/m) and 59.19% of them are strongly saline (ECe > 16 dS/m). The high content of soluble salts, especially in the surface and sub-surface layers, could be attributed to the absence of leaching due to the scarcity of rainfall and the barren nature of the study area.
• In most soil samples, soluble cations are dominated by sodium followed by calcium, magnesium and then potassium. Exceptional cases are found in some soil samples which calcium exceeds sodium. The soluble anions are characterized by the dominance of chlorides followed by sulphates and bicarbonates, while the soluble carbonates are absent. The results also indicate that the soluble cations and anions are very wide in the range and distribution among the different locations.
• The organic matter content of the studied soil samples is very low and varies between 0.05 to 0.98%. The much lower values of organic matter in this area may be due to the aridic moisture and hyperthermic temperature regimes and the poor of natural vegetation.
• The calcium carbonate content of the investigated soil samples differs from 11.74 to 48.46%. In other words, about 0.74% of the soil samples are moderately calcareous, 43.38% are strongly calcareous and 55.88% are extremely calcareous soils. The surface layer has a relatively higher calcium carbonate content than the subsurface ones in most soil profiles. The high contents of CaCO3 reflect the calcareous parent material nature of these soils.
• These soils have a low concentration of gypsum that ranges from 0.23 to 6.76%, indicating that these soils were developed from parent materials that were poor in gypsum.
• The cation exchange capacity (CEC) of the studied soil ranges from 3.10 to 28.00 cmol(+)/kg. In most cases, the low CEC values of these soils are due to the dominance of coarse texture, while some high CEC values occur in the soil layers that contains high fine materials and low organic matter content.
• The exchangeable sodium percentage (ESP) of these soils changes from 7.50 to 16.80%. Most of the soil samples (66.18% of the soil samples) have ESP value of less than 15% indicating non-sodic samples. Only 33.82% of the total studied soil samples are sodic and have ESP values greater than 15%.
2 – Soil Fertility Status
• The available soil nitrogen (N) of the study area varies between 2.30 and 88.8 mg/kg. Most of these soils (85.71%) show low available nitrogen levels that are less 40 mg/kg while, 14.29% of the total area have medium nitrogen ones (40- 80 mg/kg). Low contents of available N in these soils may be due to the poor organic matter content.
• The available soil phosphorus (P) of the study area ranges between 2.89 and 9.53 mg/kg. About 59.18% of the study area show low available phosphorus levels that are less than 5 mg/kg, 40.82% of the total area have a medium level of available phosphorus that between 5 and 10 mg/kg.
• The available potassium (K) of the study area differs from 57.3 to 535.6 mg/kg. About 28.57% of the investigated soil profiles are low (<135 mg/kg) in the available potassium, around 55.10% of the total study area have a medium available K content (135- 335 mg/kg) and 16.33% are high in the available K levels that have >335 mg/kg. The highest levels of available potassium are recorded in the silt loam and loam textures, whereas, the lowest ones occur in the coarse-textured soils. The medium and high levels of available potassium in most soils may be from the feldspar of the parent material.
3 – Soil Classification
The soils of wadi Qena lie within the arid region. Accordingely, the soil profiles lack many of the morphological features and horizons that reflect a relatively weak type of pedogensis. In terms of the presence and absence of accumulation zones, soil understudy (the middle part of wadi Qena) could be distinguished into three types namely, the soil that are devoid of perceivable zones, soils that acquire lime accumulation zones and the soil that have salt accumulation zones. These features reflect the influence of the torric moisture and hyperthermic temperature regimes that are evidenced by weak horizon differentiations for salic and calcic horizons in some locations.
The studied soils are classified into different taxonomic unit at the subgroups and the family levels according to soil taxonomy (Soil Survey Staff, 2014). The recognized subgroups are, Typic Quartzipsamments, Typic Torripsamments, Lithic Quartzipsamments, Typic Torriorthents, Typic Haplosalids, Calcic Haplosalids, Typic Haplocalcids and Sodic Haplocalcids. The great groups representing the study area are mapped. These soil taxa are further differentiated to soil families according in to particle size class, mineralogy and temperature regime. Accordingly, twenty-five families were recognized within Entisols and Aridisols orders (7 and 18 families, respectively).
4 – Land Capability Evaluation
The land capability of the investigated area for agricultural use was evaluated using the applied system of land evaluation (ASLE) software (Ismail and Morsi, 2001) and modified Storie index (O’Geen et al., 2008). The results revealed that:
a- According to the ASLE software, the soils of the study area are fair, poor (C4), very poor (C5) and non-agricultural (C6) classes for agricultural use due to some limiting factors. About 55.10% of the total study area are poor (C4) 18.37% are very poor (C5) and about 26.53% are considered as non-agricultural (C6).
b- Using the parametric approach of modified Storie index rating (O’Geen et al., 2008), the land capability of the studied soils are classified as fair (grade 3), poor (grade 4) and non-agricultural (grade 5) classes for the agricultural use due to some limtations. About 10.20% of the total study area are fairly capable and 28.57% are poor (grade 4) and about 61.23% of these soils are not suitable for the agricultural use (grade 5).
The main limiting factors of the study area for irrigated agriculture were coarse texture, high salinity, high CaCO3 content and sodocity (sometimes) in descending order.
The application of ASLE program after implementation of some management practices, the land capability of the study area could be improved for better classes. So, about 89.8% (5582.96 hectares or 13288.51 feddans) of the total area could be a fair class (C4) and the area that is very poor (C5) will be reduced to 10.2% (634.14 hectares or 1509.39 feddans). On the other hand, the area is non-agricultural suitable disappeared after applying these management practices, resulting in improving its current land capability to be potentially capable.
In addation, applying the management practices, using modified Storie index system, the land capability of the study area could be improved resulting in 8.16% (507.31 hectares or 1207.51 feddans of the total area to be of a good capability class (C2), 42.86% (2664.65 hectares or 6342.38 feddans) to show a fair class (C3) and 46.94% (2918.31 hectares or 6946.13 feddans) to have a poor class (C4). Also, the area that is non-agricultural suitable will be reduced to 2.04% (126.83 hectares or 301.88 feddans) of the total area.
5 – Land Suitability Evaluation
The applied system of land evaluation (ASLE) program for arid and semi-arid regions and Sys et al. (1991 and 1993) was used to determine the suitability of the studied soils for growing twenty five field, forage, vegetables crops and fruit trees. The studied soils have a wide range of suitability. The results showed that the suitability of those soils for most proposed crops varied from suitable (S2) to not suitable (NS1) class for the selected crops due to presence of some soil limiting factors.
According to ASLE program the results show that the highly suitable class (S1) is recorded for olive trees. Moreover, the suitable class (S2) is registered for date palm. However, the moderately suitable class (S3) is found for grape, pear, fig, barley, wheat, sugar beet, sunflower and green pepper. On the other hand, the currently not suitable class (NSI) is listed for pea, soybean, apple, faba bean, sorghum, maize, peanut, potato, tomato, alfalfa and watermelon. Meanwhile, the permanently not suitable class (NS2) is selected for rice, cotton, onion and cabbage.
According to the Sys et al. (1991 and 1993) rating tables, the soils that show a highly suitable class (S1) are assigned for growing olive, grapes and watermelon, and. However, the currently not suitable (N1) is allocated for sesame and sorghum. On the other hand, the permanently not suitable (N2) class is given for faba bean, onion, soybean, rice, carrot, green pepper, citrus, wheat, tomato, cowpea, mango, pea, white potato, cabbage, sweet potato, alfalfa, sunflower, barley, maize, sugar beet, guava, cotton and sugar cane.
In conclusions, it is obvious that this study declares the following points:
a- The soils of the study area will offer great potential for sustainable irrigated agriculture use if good agricultural management practices are applied to decrease its limitations.
b- The land spatial modeling which is based on the applied system of land evaluation (ASLE) program for arid and semi-arid regions is preferably used for evaluating land capability and suitability of an area compared to the other land capability approaches due to its compatibly with to many Egyptian conditions.
c- The main limiting factors of the studied soils for irrigated agriculture are the high salinity, high calcium carbonate and high ESP values as well as coarse texture and low levels of available nitrogen and phosphorus. So, to improve these limitations could achieving sustainable agricultural use of these soils it is recommended to apply the following:
1- Continuous additions of organic matter as well as organic and inorganic ferttlizers to improve the properties and the fertility of these soils as well as reducing the negative effect of calcium carbonate.
2- Introducing sprinkler and drip irrigation systems to the study area with reducing the irrigation periods to avoid salt accumulation on the soil surface. So, a drip irrigation system is a good way to improve practice on the coarse-textured soils, which maximizes the water use efficiency.
3- Salinity limitation could be eliminated by reclaiming these soils through salt leaching especially if a good quality irrigation water is available, the application of gypsum and other management practices as well as, the use of proper cropping pattern could improve the properties of these soils.
4- Selection salinity tolerant crops should be taken into consideration to be grown in the study area since some of the studied soils are suffering from salinity.
d- Growing wheat, barley, faba bean, sugar beet, sunflower, alfalfa, pepper, watermelon, grape, olive, apple, fig and date palm which are considered the suitable crops for the irrigated agriculture in the study area.