Changes In Several Soil Chemical Properties Following Amendment With Olive Mill Waste Water Sludge

Abstract

Abstract Olive oil extraction produces large amounts of waste water, known as olive mill waste water (OMWW). This sludge has a high chemical oxygen demand and contains high level of phenolic compounds and is therefore a cause of environmental pollution. The exploitation of this waste without preliminary treatment is very limited considering its toxicity for soils and plants. In Tunisia, 700,000 tons of OMWW, produced annually, are generating many types of pollution. They are dried in special basins and then put in heap to be used as compost while an important fraction of the product is poured directly in the natural channel.It is within this framework that this work has been carried out aiming at finding new technologies or processes for the treatment and the valorization of this effluent. The spreading of Margines on sandy soil in Southern Tunisia represents an interesting alternative for this sewage.The aim of this work is to assess the short term effect of OMWW (olive mill waste water) application on chemical soil properties. In fact, the application of 50 (T1), 100 (T2) and 200 (T3) m3/ha of this wastewater resulted in a significant improvement of soil fertility due to its richness in organic matter such as N and P.Application of three doses: 50, 100 and 200 m3∙ha−1 of OMWW increased the soil electrical conductivity significantly with the increase of OMWW rates at the depth 0 - 25 cm. The pH variations were not detected during the experience. Furthermore, soil sodium, chlorides and sulfates values were substantially affected by OMWW salinity. The ratio C/N increased from 9.45 observed for the control sample to 12,91, 18,25 and 22,5, respectively, with the increase of OMWW rate in the top layer (0 - 25 cm). The both exchangeable and total potassium increased gradually with the OMWW application dose.