Effects of compost, olive mill wastewater and legume cover cropson soil characteristics, tree performance and oil quality of olive trees cv.Chemlali grown under organic farming system

Abstract Utilisation of compost, olive mill wastewater and legume cover crops in an organic mature olive grove cv Chemlali was tested from 2013 to 2015 cropping seasons. Olive trees were subjected to one of the following treatments: TC: control, no amendment; TP: olive trees amended with compost, TM: olive trees amended with organic olive mill wastewater and TF: olive trees intercropped with legumes (Fava bean). The effectsof these treatments on soil characteristics, physiological traits, nutritional status,growth and oil yield and also the quality of the olive oil were evaluated at the end of the experiment and compared to the control. The most important effects on soil characteristics included a significant increasein the N, P, K availability and an increase of soil organic matter content. The compost amendment resulted tothe most significant increase in the soil water content and olive tree performance, mainly maximum yield of photosystem II (Fv/Fm) and the stimulation of olive tree growth and yield. The use of olive mill wastewater (OMW) increased the leaf Na + concentration and reduced significantly the electron transport rate (ETR) of olive trees. Compared to TC, all organic amendments improved significantly the oil yield by about 55, 70 and 100% inTM, TF and TP plots, respectively, however oilquality still within the threshold limits set for an ‘Extra virgin’classified olive oil.