Six transects were taken across the Nile valley in the east-west direction in Assiut Governorate in order to determine the different forms of iron and manganese in these soils. Surface soil samples were collected from an average of 6 locations in each transect in the winter of 2003/2004. Six forms of Fe and Mn were determined, exchangeable (Exch.), carbonate bound (Carb.), Mn oxides bound (MnOx), organic bound (O-bound), poorly crystalline iron oxides bound (PCFeOx) and crystalline iron oxides bound (CFeOx) along with the total content of both elements. The residual fraction was calculated by the substraction.
Values of Fe in the carbonate form ranged from 0.00 to 11.25 mg/kg (0.007% of the total Fe). Concentrations of Fe in Mn oxide and organic bound forms represented 0.018 and 0.009% of total Fe, respectively. About 34% of the samples contained less than 1000 mg/kg of Fe bound to the poorly crystalline iron oxides, while 23.7% contained more than 2000 mg/kg. Values of Fe in the crystalline Fe oxide form ranged from 740 to 17914 mg/kg (15.52% of the total Fe). Residual Fe in soils under study had values varied between 8.36 and 94.67 g/kg with an average of 45.63 g/kg (82.11% of the total Fe). The content of the total Fe ranged from 9.73 to 105.52 g/kg with an average of 55.58 g/kg.
Levels of Mn in the soluble + exchangeable forms (Exch.) ranged between 1.20 and 13.20mg/kg (0.51% of the total Mn). Values of Mn ranged from 14.25 to 78.00 mg/kg (4.29% of the total Mn), 26.00 to 420.00 mg/kg (28.88% of total Mn) and 6.00 to 324.4 mg/kg (20.00 % of the total Mn) in the carbonate, Mn oxide and organic forms. Concentrations of Mn in the poorly crystalline Fe oxide form varied from 2.50 to 125.60 mg/kg (6.07% of the total Mn). The values of residual Mn ranged from 31.60 to 581.90 mg/kg (35.06 of the total Mn). Values of total Mn in the tested soils ranged from 149.20 to 1310.00mg/kg.