The effects of a seaweed extract in addition to nitrogen and boron fertilization on productivity, fruit maturation, leaf nutritional status and oil quality of the olive (Olea europaea L.) cultivar Koroneiki

BACKGROUND: There is not adequate literature on effects of seaweed extracts (SWE) on yield and nutritional status of olive trees as well as olive oil quality. In this work, a study of the effects of a seaweed extract applied foliarly (0.5% v/v) in addition to soil application of N (500 g NH4NO3 per tree) and B (150 g borax per tree) on productivity, fruit parameters, nutritional status and olive oil quality of a Greek olive cultivar was performed. RESULTS: In contrast to the trees treated with N (NH4NO3) or N + B (NH4NO3+ borax), the additional application of seaweed extract (treatments N + SWE and N + B orax + SWE) increased the productivity and oil content and accelerated maturation of the olive fruits. In particular, the best results concerning productivity, oil content and earliness of maturity (colour and firmness) were observed in the trees treated with N + B + SWE. The additional application of SWE also increased K, Fe and Cu concentrations and reduced the concentrations of Mn in olive leaves compared to the corresponding treatments without SWE. Total phenol concentration in oil was minimized in all fertilization treatments but, particularly, the additional application of SWE did not affect it. The application of N + B + SWE led to a significant increase in linolenic as well as oleic acid concentrations, and to a decline in palmitoleic, stearic and linoleic acid concentrations in olive oil. CONCLUSION: The fertilizer treatments of this experiment and especially the combination of NH4NO3+ borax + SWE should be recommended for the studied olive orchards, in order to increase tree productivity and improve their nutrition status and various olive oil quality parameters. (c) 2009 Society of Chemical Industry