Thesis (M.Sc.) - Cairo University - Institute of African Research and Studies - Department of Natural Resources

A field experiments with two different soil types (sandy and calcareous soils) under greenhouse conditions to study the effect of sludge on two different soil characteristics and wheat yield. Results revealed that soil organic matter, water-holding capacity, cation-exchange capacity, electrical conductivity, and concentrations of available N, P, and K increased under composted sludge treatments.However, total carbonate, soil pH, and bulk density decreased with increasing application rates of composted sludge. However, higher composted sludge rate (10 ton/ha) exhibited significant accumulation values for heavy metals particularly Pb and Ni. Therefore, fertilization rate with composited sewage sludge must be lowered to 2 or 4 ton/fed, to avoid possible contamination of wheat grains.Although the application of composted sewage sludge by mixing it with the top 30 cm soil layer was found to be more effective in improving soil physical, chemical and fertility conditions of the soil and increased nutrients that required for plant to increase its growth, however, heavy metals accumulation in both soil and plant is consciously considered a serious problem. Accumulation was mainly associated with Pb and Ni at (10t/fed) rate. Therefore, although composted sewage sludge introduced significant increase in providing plant with macro and micronutrient elements, however, care should be taken in the addition of high sludge rates to avoid soil and plant contamination and hazard pollution

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