Afify, A. A.; M. M. Soliman; Mona K. M. Abdel-Razek and Hanan E. M. El Azab( 2019). Monitoring Land Degradation Impact on A Unique Agrobiodiversity in Siwa Oasis, EgyptJ.Soil Sci. and Agric. Eng., Mansoura Univ., Vol. 10 (3):157 - 171 , 2019
Abstract: The study area is situated in north-west of Egypt. Physiographic units were delineated using satellite data of TM5 and TM8, in the years 1986 and 2018, respectively. They are mesa, pediplain (partly cultivated or waterlogged), aeolian plain (partly cultivated or waterlogged), aeolian dunes and ponded areas (artificial lakes). Other features are those of settlements and roads. Extra ponded areas from 1986 to 2018 covered 159.38, 80.56, 5296.6, 8.37, 6.70, and 34.37 hectares over pediplain, pediplain (cultivated), pediplain (waterlogged), aeolian plain and aeolian plain (cultivated) respectively. Extra waterlogged areas from 1986 to 2018 covered 4917.61, 1273.21, 3887.37, 205.32 and 23.50 hectares over pediplain, pediplain (cultivated), aeolian plain, aeolian plain (cultivated) and aeolian dunes respectively. Generally 5585.97 and 10307.0 hectares have been ponded and waterlogged respectively with total land degradation of 15892.97 hectares. Soil drainage classes versus soil taxonomic units are: (a) Excessively drained soils in aeolian plain and aeolian dunes have Typic Torripsamments, mixed (calcareous). (b) Well drained soils in the cultivated pediplain are dominated by Typic Haplocalcids, fine loamy, mixed. In cultivated aeolian plain are Xeric Torripsamments, mixed (calcareous). (c) Moderately well drained soils in pediplain are dominated by Calcic Haplosalids, coarse loamy, carbonatic, while in the cultivated area are dominated by Aquic Haplocalcids, coarse loamy, mixed. In cultivated aeolian plain, the soils are Oxyaquic Torripsamments, mixed (calcareous). d) Poorly drained soils in pediplain are dominated by Calcic Aquisalids, fine loamy, mixed, while in aeolian plain are Typic Aquisalids, sandy, mixed. (e) Very poorly drained soils are Gypsic Aquisalids, fine loamy, mixed in the pediplain but are Gypsic Aquisalids, sandy, mixed in the aeolian one. Land Utilization Types (LUTs) of date palm, olive and jojoba using drip irrigation were currently evaluated under soil limitations of calcareousness, drainage condition, salinity and sodicity. This current suitability can be potentially more profitable after executing land improvements for drainage, salinity and sodicity. Whenever the action of replacing surface irrigation by drip one, current cultivation expansion must be conditioned under drip irrigation in the aeolian plain. It is potentially highly suitable for olive and jojoba. Being this plain aligning the southern borders of the lakes, it has an easy access to be supported with the recycled water as subtracted from those lakes. The cultivation expansion will be more profitable for jojoba as being highly tolerant plant for salinity and marginal fertility. This water and land practice in that aeolian plain will reduce the problem of current and later on land degradation. Formal water management become a must by saving water use as well as realizing its recycling use.
Keywords: (Siwa Oasis, physiography, soil drainage, soil classification , land degradation .)
