Olive oil mill wastewater for soil nitrogen and carbon conservation

In this work the application of two levels of N fertilizer (NH4NO3) dissolved in water or olive oil mill wastewater (OOMW) diluted 10 or 20 times in water, has been studied in relation to the properties of two soils (Loam and Silt-Clay-Loam). Also, the effect of irrigation water bubbled with CO2 (Dissolved Inorganic Carbon, DIC) was studied. Nitrate N, ammonium N, total N, organic C (OC), and CaCO3 contents were determined in the soil as well as pH, electrical conductivity (EC), oxidation–reduction potential (ORP), and absorbance at 250 and 360 nm.Our data provide evidence that inorganic-N fertilizer dissolved in OOMW significantly reduced the emission of nitrates from soils for two months, increasing OC values. Moreover, OOMW significantly lowered the ORP. The irrigation with DIC also increased soil OC. Thus, the application of inorganic-N fertilizers dissolved in OOMW diluted with water on soils and the irrigation with water bubbled with CO2 could reduce the environmental impact of OOMW, nitrates, and CO2.