Effect of olive oil mill wastewater application on soil biological properties, oil quality and fruit yield of two cultivars of olive

Olive mill wastewater (OMW) in three phase system is a byproduct of olive oil extraction with high pollution load. Since it has a lot of water, organic matter and plant growth nutrients, can be used as a solution for disposal of it in olive groves. In this study, the olive trees cultivars Zard and Local Roughani (Roughani) were treated by different levels of OMW (0, 90, 190 and 380 L Tree-1) for two years. The experiment was carried out as factorial in a randomized complete block design in Manjil region, Guilan province. Results showed that, OMW application especially in high levels increased organic carbon, microbial respiration, microbial biomass carbon and soil dehydrogenase enzyme activity in soil and it has a positive effect on the fruit yield. Also, it improved the quality of olive oil in terms of free fatty acids and peroxide value in olive oil, but not effect on the oil percent in dry matter. Biological characteristics in soil were different under two cultivars cultivation. Also, there was a significant difference between two cultivars in oil quality characteristics. Quality characteristics were in the range of virgin and extra virgin olive oil, in both cultivars under treated with OMW.