Evaluation of the effects of short-term amendment with olive mill pomace on some soil properties

The extraction of olive oil produces an enormous quantity of waste, such as olive mill wastewater (OMWW) and olive mill pomace (OMP), The majority of the agricultural wastes, including olive oil mill waste, are used as soil amendments due to their high nutritional value. The purpose of this study was to investigate the effects of the amendment with olive mill pomace from a 3-phase cold-pressed system on the characteristics of the soil pH, electrical conductivity (EC), and organic matter content (OM). The experiment was carried out using increasing rates of olive mill pomace (12.5%, 25%, 50%, 75%, and 100% w/w) plus the control untreated soil in microcosms under laboratory conditions. The results showed that the treatment of soil with olive mill pomace has a significant effect on soil properties (pH, EC, OM, OC, and CaCO3) soil pH was decreased under OMP treatment, especially with high doses of PR4 and PR5, and the electrical conductivity of the soil (EC) was increased, as well as soil carbonate content. Moreover, the soil organic matter content and soil organic carbon content were highly increased under the treatment with OMP. As a result, we can consider the olive mill pomace as a soil fertilizer. Pretreatment of olive mill pomace to reduce acidic pH and salt content before use as a soil amendment is also recommended.