EFFECTS OF PELLETIZED SEWAGE-SLUDGE ON SOIL PROPERTIES OF A CRACKING CLAY FROM EASTERN AUSTRALIA

The effects of applying varying rates (0-250 g kg(-1)) of pelletized m ixtures of sewage sludge and other waste materials (peat and cotton '' gin trash'') on the soil physical and chemical properties of a crackin g clay from Eastern Australia was investigated in a laboratory study. Soil properties measured were pH, electrical conductivity, nitrate-N, organic C, exchangeable cations, aggregate density, dispersion and geo metric mean diameter aggregates formed after soil had been puddled and dried. In comparison with untreated soil, application of the pellets increased soil acidity, electrical conductivity, nitrate-N and organic C, and decreased exchangeable Ca and Na. Partial substitution of sewa ge sludge and peat with cotton ''gin trash'' reduced the intensity of the above changes in soil properties. Changes in soil physical propert ies were limited to a small decrease in soil density. Addition of pell etized sewage sludge/waste material mixtures to a cracking clay had si gnificant short-term effects on soil chemical properties but limited e ffects on soil physical properties. (C) 1996 ISWA