Effect of composted olive mill solid waste on oil percentage and quality of olive oil cvs Zarad and Roughany on Manjil region

Olive mill solid waste is enriched from organic matter and mineral nutrient elements, which can be used after compostation for inproving soil fertility and solve its disposal problem. For this purpose, a factorial experiment was carried out during 2013 to 2015 in Manjil region. The treaments were different levels of composted olive mill solid (12, 24 and 36 kg per tree and followed by 15 kg per tree rotted sheep manure as a control) which used on two oilve cvs Zard and Roughany. The results showed that there was no significant difference for oil percent between control and different level of compost after first year, but on the second year, olive tree treated with 36 kg compost showed significantly 5.71 oil percent more than other treatments. There was no significant difference between different leveles of compost and control for oil free fatty acids and absorption in the ultraviolet wavelengths (K232 and K270) over two years. In the second year, the trees that had been treated by 24 and 36 kg of compost, had a better oil quality form which peroxide value was less as compered to other treatmentes. On the second year, oil quality from which flavonoid content in olive tree treated with compost was significantly better than control. However, on this year, oil chlorophyll and carotenoid content of coltrol was higher than compost treated tree, but no significant differenec was found between compost treated trees and control for the ratio of oil chlorophyll to carotenoids content. There was a significant difference between two olive cultivars, Roughani and Zard for oil free fatty acid, peroxide value, K232 and K270, phenols, flavonoids, chlorophyll carotenoids. Overall, the oil quality of both olive cultivars which treated with manure and compost was in the range of extra virgin olive oil, based on standards of the International Council of Olive Oil at two years.