Set of Agricultural Land Evaluation in El–Dakhla Oases Soils, Egypt

 
 
 
EL–DAKHLA Oases soils are located between longitudes 28^O   30 ^-  and 29^O  04 ^-  East and latitudes 25 ^O  20^-  and 26 ^O  00 ^-  North, covering about 2000 km².
 
Physiographic mapping units, soil taxonomy, statistical size parameters, water resources quality and its suitability for irrigation and crop water requirements were performed as a set of agricultural land capability and suitability evaluation of El- Dakhla Oases soils. 
 
Land sat ETM image (2010), digital elevation model (DEM) and 3D –GIS techniques were used in ERDAS image 9.2 software to produce the physiographic map of the studied area. The main physiographic units and its soil taxonomic ; family levels could be classified as follows:
1-    Soils of Playa:
a-     Typic Haplosalids, fine loamy over sandy skeletal, mixed, hyperthermic.
b-    Duric Haplosalids, sandy skeletal, mixed, hyperthermic.
2-Soils of Sabkha:
Lithic Gypsisalids, sandy skeletal, siliceous, hyperthermic, shallow.
3- Soils of Sand Sheets:
Calcic Haplosalids, sandy skeletal, mixed, hyperthermic, deep.
4- Soils of Peniplain:
Typic Haplosalids, clayey skeletal, hyperthermic.
5- Soils of Cultivated plain:
a- Typic Torriorthents, fine loamy, mixed, hyperthermic.
b-Typic Torriorthents, clayey over fine loamy skeletal, mixed, hyperthermic.
c-Typic Haplosalids, coarse loamy skeletal over clayey, mixed, hyperthermic .
d-Typic Haplosalids, fine loamy over coarse loamy, mixed, hyperthermic.
 
The statistical size distribution reveal that these soils have mainly  poorly sorted sediments with near symmetrical to fine skewed materials and lepto kurtic to meso kurtic pattern. These parameters indicate that the studied area is formed under water or both water and wind action, forming of non- uniform parent materials.
 
Current suitability of the studied soils could be categorized into three suitable classes; moderately suitable (S₂) , marginally suitable (S₃) and not suitable (N₁) with different intensity degree of soil limitations. By existing suitable improvement practices, the potential suitability classes assessed are two suitability classes; moderately suitable (S₂) and not suitable (N₂).
 
Data revealed that current suitability for some specific crops were not suitable (N), except for some scattered areas developed on cultivated plain which are suitable for all the studied crops. On the other hand, the potential suitability classes differed according to the satisfaction conditions between different properties of soils developed on the studied physiographic units and crop water requirements. However, soils of sabkha and cultivated plain are highly suitable (S₁) for groundnut. Also, soils of peniplain and cultivated plain are highly suitable (S₁) for potato and grapes. Whereas, soils of playa, peniplain and cultivated plain are moderately suitable (S₂) for olives.
 
Water of wells and springs are considered the main sources for irrigation in El- Dakhla Oases soils. Data revealed that the suitability of irrigation water had (C₁–S₁) class with non restriction at west El–Mowhob and Kalamon area , while it represented (C₄–S₄) class with very high salinity levels and very high alkalinity hazard at El- Zaiate well and Bathor spring waters, indicating severe restrictions in these soils.
 
Data revealed that the crop water requirement values of some specific crops are considered high, due to the highness of evapotranspiration values. It represented with an average of 500, 800 and 1800 mm/s for vegetable, field and fruit crops, respectively. So, it is very important to apply suitable irrigation systems such as trickle or sprinkler, under these conditions.