SOIL TAXONOMIC UNITS AND MICRONUTRIENTS CONTENT OF BAHARIYA OASIS, EGYPT

Abstract

The relationship between some extractable micronutrient contents i.e., Fe, Mn, Zn,Cu and B and their relation to the soil taxonomic units of an area south east El-Bauity in El-Bahariya Oasis, Egypt are study. Twenty one representative soil profiles and eighteen pits were dug in the study area and classified to the soil family level according to the Soil Taxonomy USDA (2010). The obtained results are summarized as follows: The studied area belongs to tow orders, four suborder, sixteen families as follow: - Order Aridisols includes two suborders i.e., salids and gypsids - Order Entisols has two sub orders orthents and psamments. Order Aridisols covers ten soil families, their texture range from loamy sand to clayey, whereas order Entisols contains six families their soil texture is sandy to sandy loam soils. Generally the soils of order Entisols have high percent of sand fraction and Fe content, averages are 74.6 % and 4.93 µg g-1 respectively, but have low averages of organic matter, gypsum, lime contents and other micronutrients. Whereas soils of order Aridisols have high averages of clay content and all other variables except Fe. Soils of Aridisols contain higher amounts of micronutrients Mn, Zn, Cu and B than in soils families of Entisols, but in contrast values of Fe are much higher in Entisols as compared to Aridisols . Averages of DTPA extractable amounts of Fe, Mn, Zn, Cu and B in Aridisols samples ranged between 2.9, 3.2, 2.1, 1.1 and 2.5 µg g-1 respectively, while the corresponding values in Entisols are 5.6, 2.7, 1.9, .6 and 1.3 µg g-1, respectively. Some values are greater than the marginal levels reported in the literature i.e. about 12 % for Fe, 84 % for Mn, 20 % for Zn, 36 % for Cu and 8 % for B in soil families of Aridisols respectively, whereas in Entisols soils were 40.9, 95.5, 9.1, 4.6 and 5.2 % for Fe, Mn, Zn, Cu and B, respectively. Both orders have averages of some micronutrients lower than the critical levels i.e. about 43.9 % for Fe, 81.2 % for Zn, 64.9 % for Cu and 33.5 % for B.