Physical Characterization of Some Libyan Soils in Sidi El Mesri Area in the Jaffara Plain

الملخص

The soil types that are observed in Sidi El Mesri area of‘the Jaffara Plain have the following characteristics. (1) Ridge Soil occupies all the ridge and hilly areas. The soil in these ridges is deep loose soil, sandy loam in texture, with low content of Ca CO3. The distribution of Ca CO3 is more of less uniform with depth. (2) Valley Soil occupies all the nearly level area between ridges. This soil is more developed compared with Ridge Soil. Ca CO3 content is higher, with more Ca CO3 content in the subsoil in concretion form. Because these valleys form depressions which are surrounded by hilly sloping land, it receives water runoff. The soil is deep sandy loam in texture, and the subsoil is a little compact when dry but friable when moist. (3) Sloping Soil which is similar in character to Valley Soil except that it has a strongly to moderately sloping surface. Calcipan Soil, which contains zone of accumulation of Ca CO3 in the subsoil. This layer is cemented and the Ca CO3 content reaches up to 60%.
The soils in the area of study are developed from alluvial material washed mainly from sandstone and sand shales.
All types of soils are low in salt content and there is no trend of salt accumulation with depth except in the Calcipan Soil. The soil reaction is generally neutral, but slightly alkaline in the calcipan horizon. The bulk density of soils does not indicate any compaction problem even in the zone of accumulation of Ca CO3. The water is retained in soils with low potential and most of it is released from soil under low suction, which indicates that large size pores are dominant in the soil.
The water holding capacity of the soil is low. When the Ca CO3 content is high as in the zone of accumulation of Ca CO3, the water holding capacity is comparatively high. Generally speaking the water which is held in that soil at field capacity is about 10 % on volume basis, and is approximately twice the water which is held in soil at wilting point.