Responses of young olive ('Koroneiki') plants treated with organic and inorganic fertilizers

Two-year-old, self-rooted olive (Olea europaea L. 'Koroneiki') plants were tested. The potted plants were grown in two types of soil: neutral (AC) and alkaline (AL), and they were fertilized with a liquid organic product containing fulvic and humic acids and with inorganic fertilizers, following seven treatments: AC1 & AL1: no application; AC2 & AL2: nitrogen application; AC3 & AL3: application of the organic product (1.66 mL kg^‑1 soil) at the petal fall stage (PFS); AC4 & AL4: application of the organic product at the PFS and 20 days after the PFS; AC5 & AL5: application of the organic product at the PFS, 20 and 40 days after the PFS; AC6 & AL6: application of nitrogen and potassium (2.5 g K₂O plant^‑1); AC7 & AL7: application of nitrogen and potassium (5 g K₂O plant^‑1). In winter, nitrogen (5 g plant^‑1) was applied as granular fertilizer (type 26-0-0, calcareous nitric ammonium for the neutral soil; type 21-0-0, ammonium sulfate for the alkaline soil) and K as potassium sulfate (type 0-0-50 for both types of soil). The results showed that fertilization affected the vigor, physiological and nutritional parameters of plants. The above parameters were also greatly influenced by both soil type and the interaction of soil and treatments. In addition, experimental data showed that the organic treatments, in both soil types, had a positive effect on shoot length (AC5, AL5) and number of olive fruits/plant (AC3, AL3, AL4). Finally, inorganic nitrogen-potassium fertilizers (AC6, AL6) increased the concentration of total chlorophyll in leaves.