Agriculture & Food, Volume 8, 2020

Abstract: Forty-year-old, self-rooted olive trees (Olea europaea L. cv. Koroneiki) were assessed in Messinia district (southern Greece). Trees were grown in two types of soil: acidic (AC) and alkaline (AL) and they were fertilized through foliage with a liquid organic product containing fulvic and humic acids, following four different schedules: Treatments AC1 & AL1: No application of organic product; Treatments AC2 & AL2: Foliar application of organic product (0.5% v/v) at the petal fall stage; Treatments AC3 & AL3: Foliar application of organic product at the petal fall stage and 20 days after the petal fall stage; Treatments AC4 & AL4: Foliar application of organic product at the petal fall stage, 20 and 40 days after the petal fall stage. In all treatments, 0.8 kg N/ tree were applied as granular fertilizer (type 21-0-0, ammonium sulfate for acidic soil; type 26-0-0, calcareous nitric ammonium for alkaline soil), on 20 January 2019. The results showed that AC4 treatments significantly enhanced the vegetative vigor of trees (new shoot length), whereas the other organic treatments in the acidic soil did not appear to affect it. Moreover, the experimental data showed that AL3 treatment resulted in an increase (without statistical significance) in the leaf concentration of chlorophyll a, b, whereas AL4 treatment led to a decline in the leaf carotenoids concentration. Significantly increased concentrations of chlorophyll and carotenoids in alkaline soils compared to acidic ones were observed. At the harvest period, olive fruit weight was significantly higher in AC2 and AL2 treatments.