Effects of Sewage Sludge and Sludge Compost Applied to Soil on some Soil Physical and Chemical Properties

Abstract

AbstractThe effects of different application rates of sewage sludge and sludge compost (0, 40, 80, 120, and 240 metric tons/ha) on soil physical and chemical properties were studied at two pH levels.Sludge application rates exceeding 120 metric tons/ha were difficult to apply and produced a cloddy seedbed, while the same rate of compost was easily applied and produced a friable seedbed. Sludge and compost increased the water content and the water retention of a silt loam soil. Both the sludge and compost increased the salinity and chloride levels of the soil to a level which may affect salt‐sensitive plants. The soil's cation exchange capacity increased as much as threefold as a result of the addition of sludge and compost. Nitrate‐nitrogen levels were highest at the 15–20 cm soil depth but decreased sharply below this level. Available phosphorus was high during the 2‐year study and appeared to be in excess of that needed for good crop growth.