Soil Responses to High Olive Mill Wastewater Spreading

Abstract

Olive manufacturing generates the most polluting wastewater. Olive mill wastewater (OMW) contains a large amount of organic and inorganic fractions. Olive-oil-producing countries have investigated several treatments and valorization processes for better management of this waste. The Tunisian government adopted OMW spreading on soil to manage the waste and improve the organic matter in the soil of olive groves. The examination of soil after OMW spreading was set up to assess the physicochemical changes and better comprehend the soil’s responses. An incubation of two types of artificial soil treated with 40 and 80 m3·ha−1 of OMW led to increased organic matter, phosphorus, nitrogen and potassium contents. The adsorption of the phenolic compounds in soil was dependent on the clay type and was shown by the behavior of the soil composed of bentonite clay. The germination index of tomato and alfalfa seeds recorded a positive test with OMW applied on soil, and it was in relation to the species utilized. This practice seems to be a solution for the management of OMW because it limits the use of chemical fertilizers and might be a convenient source of carbon in organic farming.