Short-term response of three soil types in Botswana to sewage sludge application

Abstract

Changes in the moisture content (MC), volatile solid content (VS), water retention capacity (WRC), bulk density (Db), porosity, pH, electrical conductivity (EC), organic matter content (OM), and cation exchange capacity (CEC) of 2 luvisols, a vertisol and an arenosol from Botswana brought about by sludge addition were investigated. Each soil type was mixed separately with a 36 months and 3 months old sludge at volume per volume percent ratios of 5:95, 10:90, 20:80, and 40:60 sludge:soil. Ninety days after sludge addition, there was an increase in the porosity, WRC, VS, CEC OM and EC of the soils and a decrease in the pH and Db. Changes were more evident in soils amended with the 3 months old sludge than in soils amended with the 36 months old sludge. Sludge application rate and soil type affected the changes observed in the pH, EC, VS Db and WRC of the different soils types. Application of sludge to these soils significantly improved their physical condition after 90 days.

Keywords: Soil physico-chemistry; sludge application rate; sludge age