Types and Distribution of Calcareous Soil in Egypt

Abstract

The calcareous soils cover a considerable portion of agricultural desert lands in Egypt, particularly in the north western coastal zone (NWCZ) and Sinai. The accumulation of carbonates in these soils is closely connected to soil genesis and formation. These soils can be defined as the soils which contain more than 14–17% total CaCO3 or more than 4–7% active CaCO3 in relation to the whole soil hydraulic properties. Some of these soils show the presence of caliche horizons. The particle size distribution of CaCO3 among the soil mechanical separates follows the textural class. These soils have variable texture sandy, loamy sand to sandy loam sandy, clay loam, silty clay loam and clay loam. The CaCO3 content varies from 10 to more than 83%. It is generally slightly and moderately to a strongly alkaline reaction where pH values of soil paste ranged from 7.4 to 9.2; organic matter content is generally low and mostly decreases with depth. Soil salinity is varies affected by agriculture system either rainfed or irrigated. In case of rainfed agriculture, it is non-saline to slightly saline, when supplemental irrigation with saline groundwater carried out the soil salinity reached to moderately saline. In case of irrigated agriculture with saline groundwater in some areas, the soil salinity reached to strongly saline. Cation exchange capacity of the soils depends on the clay percent and the CaCO3 percent in the clay and the range of 4.2 and 19.29 m.e./100 g soil. The average available soil moisture differ according to textural classes, and the value of sand, loamy sand, sandy loam, sand clay loam, and clay loam is 5.8, 7.95, 11.9, 16.33, and 24.1% respectively. The surface crust is a marked property of calcareous soils. Field observations indicated that natural crusts were quite distinctive from the soil underneath. It was massive and easily separable from the underlying soil due to the presence of relatively very thin coarse textured layer in between crust thickness, under field conditions, it varied from about 0.2 to about 1.0 cm. Seedling emergence was found to be inversely related to crust strength as well as crust moisture content. The mineral compositions of calcareous vary according to the particles size. The presence of CaCO3 and high pH level results in unavailability of phosphate and affects directly or indirectly, availability of other nutrients. Soil texture, CaCO3, are the most important factors that correlate with the total available content of the nutrients. Good soil management makes a calcareous soil produce an abundance of high quantity and quality crop yields. Poor soil management makes it unproductive. Also the selection of suitable crop for this soil is essential and vital to obtain the optimum and sustainable productivity. Appropriate management of calcareous soils requires a combination of soil and water management practices in addition to other management practices such as crop management, control weeds, pests and plant diseases. The combinations of different management practices application significantly affected the yield of most crops.