Agriculture & Food ISSN 1314-8591, Volume 8, 2020 Journal of International Scientific Publications www.scientific-publications.net Page 45 RESPONSES OF YOUNG OLIVE CV. KORONEIKI PLANTS TREATED WITH AN ORGANIC FERTILIZER Stavros Sotiropoulos 1* , Christos Chatzissavvidis 2 , Ioannis Papadakis 3 , Viktor Kavvadias 4 , Christos Paschalidis 1 , Chrysovalantou Antonopoulou 2 , Antonia Koriki 1 1 University of Peloponnese, School of Agriculture and Food, Antikalamos, 24100 Kalamata, Greece 2 Democritus University of Thrace, School of Agricultural and Forestry Sciences, Department of Agricultural Development, 68200 Orestiada, Greece 3 Agricultural University of Athens, School of Plant Sciences, Department of Plant Production Science, 11855 Attica, Greece 4 ELGO-DEMETER, Soil Science Institute of Athens, 14123 Lykovryssi, Attica, Greece Abstract Two-year-old, self-rooted olive plants (Olea europaea L. cv. Koroneiki) were tested. The potted plants were grown in two types of soil: acidic (AC) and alkaline (AL) and they were fertilized 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: Application of organic product (1.66 ml/kg soil) at the petal fall stage;  Treatments AC3 & AL3: Application of organic product (1.66 ml/kg soil) at the petal fall and 20 days after the petal fall stage;  Treatments AC4 & AL4: Application of organic product (1.66 ml/kg soil) at the petals fall, 20 and 40 days after the petal fall stage. In all the above treatments 0.42 g N/kg soil were applied as granular fertilizer (type 21-0-0; ammonium sulfate for acidic soil and 26-0-0; calcareous nitric ammonium for alkaline soil), at the beginning of the experiment. The results showed that AL4 treatments significantly amplified the vegetative vigor of olive plants (new shoot length), whereas the organic treatments in the acidic soil led to adverse results. Moreover, the experimental data showed that AL3 treatment resulted in a significant increase in the leaf concentration of chlorophyll a, b and carotenoids. Significant increase in leaf dry weight was also observed in AC4, AC3 and AL3 treatments, at the end of the experiment. Keywords: carotenoids, chlorophyll, nutrition, olive fruit, organic fertilizer, vigor 1. INTRODUCTION In Greece, the olive tree has been cultivated since ancient times, as evidenced by excavation findings. The origin of the olive tree is lost in the legends and traditions of the peoples around the Mediterranean. And this is natural, since the olive tree is so closely tied, with the history of the Mediterranean peoples, and their rational diet. Olive is the most extensively cultivated oleiferous tree species in the world, covering an area of 10 million of hectares (Yang et al., 2007). Olive oil is a great product of great economic and social importance. Its consumption is responsible for the low frequency of various chronic diseases. The beneficial properties of virgin olive oil have been attributed to the high proportion of unsaturated / saturated fatty acids, but also to some of its secondary components such as phenolic and volatile compounds from which the health benefits of olive oil arise in the Mediterranean diet (Da-Peng Yang et al., 2007). There are many studies on olive fertilization, but in some cases they are controversial. From a practical viewpoint, the fertilization requirements of olive trees depend on soil type, organic matter content, and pH. Organic fertilizers help plants grow, increase yields and improve the quality and commercial value of production while at the same time are