The current investigation aims to study the morphological, physiochemical characteristics, classification and land capability evaluation of some soils irrigated from different water sources at the north east of Tanta city El-Gharbia governorate, Egypt. Moreover, the forms of many heavy metals (Cd, Ni, Cr, Co, Pb and Fe) in these soils namely, water soluble, exchangeable and carbonate bound as well as their relationships with soil properties were determined.
For these purposes, ten soil profiles were selected representing the soils irrigated with different irrigation water sources. Three profiles were chosen representing the soils irrigated with fresh Nile water. Five profiles were selected representing the soils using agricultural drain water for irrigation. As well as, two profiles were chosen representing the soils using the mixed sewage-drainage water. The profiles were morphologically described, then soil samples were taken representing different soil layers. Moreover, ten water samples were collected from each of these water sources for integrated physical and chemical analyses. Also, soils were classified according to Soil Survey Staff (2014) and capability evaluated using ASLE model.
The studied soils are deep and well drained having almost flat topography. These soils have clay loam to clay texture grade. All studied soils are moderately alkaline and non-to slightly saline. Most of these soils haven't sodicity effect except some from those irrigated with agricultural drainage or sewage water. Most of soils have low organic matter (OM) contents except the surface layers of some from the last-mentioned soils. This could be ascribed to the factorial waste fluids and remnants in the irrigation water used for these soils. Most soils are moderately calcareous.
Most of the studied soils haven't any diagnostic horizons and classified under Entisols order and few are classified under Aridisols. The land capability evaluation indicated that, all the studied soils are considered as as good (C2). Most of the water samples have normal to slight alkalinity reaction (pH) with slight salinity hazard. Most of the agricultural drainage and all sewage waters have a slight sodium hazard and slight to moderate chloride hazard. The concentrations of heavy metals in these waters are within the permissible limits for their use as irrigation water.
The total concentration of the studied heavy metals in the studied soil was in the permissible limits. The soils irrigated with drainage and/or sewage water had noticeable higher concentrations of water soluble, exchangeable and carbonate bond heavy metals fractions than those irrigated with Nile water. The relationships of these different forms of heavy metals in studied soils with soil properties were studied and determined. Also, according to the heavy metal's mobility, enrichment and contamination factors, the studied soils are considered as moderately contaminated with these heavy metals.