Abstract
The plant-available and extractable heavy metals in a calcareous soil treated with sewage sludge from the Riyadh sewage treatment plant were investigated. Glasshouse and incubation experiments were carried out. Riyadh sewage sludge is apparently a good source of elements for plant growth. The plant-available and water-, hydrochloric acid- and DTPA-extractable metals found in sludge-treated soil were considerably higher than those found in soil alone. Fluctuations in the concentrations of chemically extractable metals with time were observed, indicating that more than one reaction process is operating and leading to more stable forms. Cropland use of Riyadh digested sewage sludge, on the calcareous soils commonly found in Saudi Arabia is unlikely to give rise to the heavy metal problems associated with disposal on acid soils. (Baker-IVI)