Influence of Olive Mill Wastewater (OMW) Spread on Carbon and Nitrogen Dynamics and Biology of an Arid Sandy Soil

Olive mill wastewater (OMW) contains large amounts of organic substances, including phenols, that can have negative environmental consequences when applied to soil. Because of the high concentrations of organic matter and mineral nutrients, OMW holds promise as a fertilizer source for cropping systems. The effects of the addition of 0.5, 1, or 2% OMW to a soil on carbon (C) and nitrogen (N) dynamics and microbiological characteristics of the soil were investigated. Mineral N presented a significant negative correlation with the amount of OMW. The total number of soil bacteria and fungi increased. However, the nitrifying population was sensitive to 2% OMW during the first month. The increase in microbiological activity accelerated the loss of soil organic carbon (SOC). However, the treated soil recovered the SOC, and the total C gains were 2.1, 1.9, and 2.4 g kg(-1) for the three doses, whereas the SOC loss was 1.1 g kg(-1) for the control.