Effect of inorganic and organic fertilization on the yield of olives (‘koroneiki') trees in acidic and alkaline soils

Two-year-old, self-rooted olive trees ( Olea europaea L. cv. Koroneiki) were assessed in Messinia district (southern Greece). The young olive potted trees were grown in two types of soil: acidic (AC) and alkaline (AL) and they were fertilized with inorganic fertilizers and organic preparation, (a liquid organic product containing fulvic and humic acids), including seven fertilization treatments through soil, as follows: · Treatments AC1 & AL1: No application; · Treatments AC2 & AL2: Nitrogen fertilization (0.42 g N/kg soil); · Treatments AC3 & AL3: Nitrogen fertilization (0.42 g N/kg soil) and application of organic product (1.66 ml/kg soil) at the petal fall stage; · Treatments AC4 & AL4: Nitrogen fertilization (0.42 g N/kg soil) and application of organic product (1.66 ml/kg soil) at the petal fall and 20 days after the petal fall stage; · Treatments AC5 & AL5: Nitrogen fertilization (0.42 g N/kg soil) and application of organic product (1.66 ml/kg soil) at the petals fall, 20 and 40 days after the petal fall stage; · Treatments AC6 & AL6: Nitrogen fertilization (0.42 g N/kg soil) and potassium fertilization with 0.21 g K₂O /kg soil (2.5 g K₂O / plant); · Treatments AC7 & AL7: Nitrogen fertilization (0.42 g N/kg soil) and potassium fertilization with 0.42 g K₂O /kg soil (5 g K₂O / plant). The results showed that inorganic and organic fertilizer treatments had a positive effect on the production of olive fruit and olive oil per plant, on the oil content and on the reduction of its acidity. The type of soil and its interaction with the treatments also play an important role.