Agricultural utilisation of lime treated sewage sludge

Over one growing season, lime treated dewatered sludge was applied to pot and field cotton cultivation at rates of 0, 10, 20 and 30 t/ha to determine the effects of sludge agricultural reuse on physical and chemical soil properties, on soil and plant heavy metal content and on plant production. In most cases total N and total and soluble P content of the soil increased with addition of sludge. Maximum pH increase caused by addition of lime treated sludge to alkaline soils did not exceed 0.2. Heavy metal content in all plant tissues and soil samples did not increase significantly as a result of sludge amendment. Plant yields increased significantly with sludge addition for the three alkaline soils used in this study. A low plant productivity observed with one of the soil types studied, was attributed to the high concentration of Ni in the soil and the low nutrient content of the soil.