Effect of solid olive-mill waste amendment on soil fertility and olive (Olea europaea L.) tree activity

► Solid olive-mill waste (SOMW) long-term effects on soil and olive trees are studied. ► Exchangeable K increases in SOMW-treated soil. ► SOMW does not have long-term inhibitory effects on the soil microflora. ► SOMW-treated trees show higher vegetative activity and olive fruit yield. ► Chemical and sensorial characteristics of the olive oil are not affected.