Matemba, Lameck Eliawony2026-06-022026-06-022001https://www.suaire.sua.ac.tz/handle/20.500.14820/7637DissertationA study was conducted to determine the occurrence of some heavy metals in sewage sludges from Morogoro and Dar es Salaam urban areas and their uptake by Amaranthus hybridus. A field study was conducted at the Horticultural Unit, Sokoine University of Agriculture Morogoro whereby, the soil was characterised for its physical and chemical properties prior to planting of the test crop. The analytical data showed that the experimental soil was texture mildly-alkaline with a pH value of 7.6, very low % O.C. The textural class of the soil was sandy clay loam. Available and total Cu, Zn, Mn. Cd and Pb ranged from medium to high as compared to established critical levels. The sewage sludge was collected from the disposing sites in Morogoro and Dar es Salaam. Prior to incorporation into the soil the sewage sludge was air dried and characterised for its chemical properties . The results showed that the available and total Cd, Mn, Cu, Zn and Pb ranged from medium to high as compared to established critical ranges. A field study was conducted to study the uptake of some heavy metals and other plants nutrients. In the field studies a Randomised Complete Block Design (RCBD) was used. The rates of sewage sludge application on air dry basis were 0, 10, 20, 40, and 60 tons/ha. Amaranthus seeds were measured by using 35 cm3 container and sowed in 1 m2 plots which were separated by 0.5 m strips while the blocks were separated by 1 m strips. The uptake of N, P, K, Mg, Ca and heavy metals (Cu, Zn, Mn, Cd, Pb) were determined. Application of sewage sludge resulted in a marked increase in metal content in Amaranthus plant especially for the highest rates of application during the first and second plantings. The uptake of other essential plant elements increased with increasing rate of sewage sludge application. No adverse effects due to application of sewage sludge were observed. At the end of the first growing season, the soil was analysed to evaluate the residual effects of sewage sludge on soil chemical properties. The results showed that sewage sludge application resulted in a marked increase in total and extractable metals as well as essential elements in the soil, except for total and extractable Mn. The application of sewage sludge resulted in a significant increase (p < 0.05) in the concentrations of Cd, Zn, Cu, and Pb. However, the metal content in the soil was below the limits generally accepted as toxic for most agricultural soils. A second planting was done in the same plots without further application of sewage sludge in order to determine the residual concentration of heavy metals in the soil from the previously applied sewage sludge. The results indicated that, the residual metal concentration in the soil had significantly increased. Plant dry matter yield of Amaranthus was determined for the first and second harvests. The application of sewage sludge from Dar es Salaam increased dry matter yield significantly (P < 0.05) at 60 tons/ha. The maximum yields obtained were 3.66 and 2.4 tons/ha for the first and second harvests respectively. The Dry matter yield as the result of application of Morogoro sewage sludge reached a maximum of 2.16 and 1.79 tons/ha at 60 tons/ha for the first and second crop respectively. Generally, the increase in theenSewage sludgesHorticultural UnitAmaranthus hybridusSewage sludgeThesis