LAUSR

Abstract The aim of the present research was to investigate the effect of two commercial organic fertilizers (Activit and Agrobiosol) on two newly planted olive cultivars for two successive years. Two cultivars were used, ‘Koroneiki’ an olive oil cultivar and “Konservolia” a table olive one. The organic fertilizers were combined with inorganic fertilizers which when used alone served as control. Organic fertilizer application resulted in lower soil pH values (8.0–8.15 compared to 8.46 in control) and higher cation exchange capacity (up to 19.6 meq 100 g−1 compared to 17.1 meq 100 g−1 in control). Soil N, K, Mn and Zn concentration were higher under the combined application of Activit plus inorganic fertilizer. A significant increase of leaf area index was observed when organic fertilizers were used. Nutrient concentrations of the leaves were in all treatments within the adequacy range. Carbon assimilation rate also increased under organic fertilization in ‘Koroneiki’ in summer (17.4–18.7 μmol m−2 s−1) compared to control (14.9 μmol m−2 s−1). Yield of ‘Koroneiki’ trees during the second year (the only cultivar bearing fruits) was higher under both organic fertilizers application, reaching almost 55% increase compared to the use of only inorganic fertilizer.