Olive orchard amended with two experimental olive mill wastes mixtures: Effects on soil organic carbon, plant growth and yield

Amendments of olive orchard soil with two different preparations of olive mill solid waste (OMWMs) at the rate of 9 ton ha−1 per year for five years in two different plots were compared with an industry standard soil amendment using urea. Both the OMWMs amendments showed significant increases in total organic carbon and humic substances in soil of approximately 40% and 58%, respectively, without negative effects on tree growth and yield. This work has shown that olive oil mill waste (OMW) can be recycled safely using the bioremediation system used in this study. We suggest that this system is particularly beneficial to organic farming and is an alternative solution to direct spreading of raw OMW on farm lands.