Study Of The Effect Of Olive Mill Waste Water Sludge On Soil Chemical Properties And On Autochthonous Pear Millet Ecotype (Pennisetum Glaucum (L) R.BR) Behavior In Southern Tunisian

The extraction of the oil produces olive mill waste water “OMWW” which has a very strong polluting power resulting in high levels of COD (chemical oxygen demand), high salinity and a strong phenolic compounds causing 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 (margines), 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. The search for new technologies or processes for recovery of the effluent is necessary.The spreading of OMWW in the sandy soils in arid conditions of southern Tunisia is a potential alternative for this purpose.In this study, spreading of 20, 40 and 60 m³/ha was tested in the presence of one autochthonous pear millet ecotype Pennisetum glaucum (L) R.Br) collected from southern Tunisia in order to assess the impact of the incorporation of this effluent on soil Chemical properties.The results of the study showed that at rate of 20 m³/ha, margines do not present risks regarding salinity, high concentrations of phenolic substances, high potassium content and pH. On the contrary, they induce an improvement of some chemical properties of the soil (organic matter content and potassium) without improving the productivity of pear millet.Application doses of Margines greater than 20 m³/ha generates a very significant decrease of yield of pear millet with disruptions of phenological stages as a result of the accumulation of phenolic substances and the excessive increase of the levels of sodium, chlorides and consequently higher levels of soil salinity in the short and long term