LAUSR

Abstract The table olive factory generates a large amount of wastewaters and this is a big environmental problem. The aim of this study was to look for a solution of this issue, using table olive waste as irrigation water during the growth of four Mediterranean crops: tomato (Solanum lycopersicum L.), strawberry (Fragaria x ananassa L.), cucumber (Cucumis sativus L.) and pepper (Capsicum annuum L.). These solutions were rich in sugars (17–85 mmoles L−1) and polyphenolic compounds (13–21 mmoles L−1), being hydroxytyrosol the main component (5.5–14.5 mmoles L−1). Also, some minerals were identified (carbon, nitrogen, sodium, potassium and phosphorus). The solutions were free of sodium chloride and no phytotoxic effect was detected, neither on the fruits or the leaves. The irrigation with the tested solutions originated an increase of the plant growth, fruit size and cumulative yield by at least 20% compared to the dipping and spraying applications mode. Also, it was observed a decrease of the powdery mildew disease in strawberry plants. Particularly, the fruit medium weight of cucumbers treated with table olive solutions was 40 g higher that the untreated fruits. Among the wastewaters generated during table olive processing, the wash water solution from Spanish-style green olives and the acidified storage liquids from black ripe olive processing could be employed as natural fertilizers and fungicide in substitution of synthetic products.