Rendimento de oliveiras e qualidade do azeite em resposta à adubação nitrogenada e potássica

Abstract

The olive tree (Olea europaea L.) is normally grown in semi-arid regions of the Mediterranean characterized by high temperatures and low rainfall. However, in recent decades, the area of olive cultivation has expanded mainly in non-traditional regions, which have different soil and climate conditions. Although the olive tree is adapted to a wide range of edaphoclimatic and soil conditions, there is a lack of information about the response of this crop to growth and production fertilization under conditions in southern Brazil, which represents the largest cultivated area in the country. The main objective of this work was to investigate the effects of nitrogen and potassium fertilization on the growth, productivity, and quality of olive oil. The work was carried out in commercial olive groves in Pelotas and Canguçu, Rio Grande do Sul, Brazil, between 2018 and 2023. For the growth phase, two studies were conducted, one with different doses of mineral N (urea) and the other with different doses of N in the form of organic fertilizer, where in both works parameters of growth, nutrition, and the first productive cycle of the plants were analyzed. During the productive phase, three studies were carried out: the first was the application of different doses of N (urea) in olive trees cv. ‘Arbequina’ and the second study was the application of different doses of K (KCl) in olive trees cv. ‘Koroneiki’, where production parameters, plant nutrition, nutrients in the soil, as well as oil yield and quality were evaluated. Finally, for the last study, the SPAD index was correlated with leaf N content in olive trees cv. ‘Arbequina’, to evaluate the technical viability of using the SPAD index to estimate leaf N content. Organic fertilization increased plant growth, improved nutritional status, and soil chemical quality. The application of mineral N promoted greater plant growth and higher leaf N content. Nitrogen fertilization in the productive phase increased the levels of foliar N, productivity, and changed qualitative aspects of olive oil from ‘Arbequina’ olive trees. Potassium fertilization increased K levels in the soil and leaves of 'Koroneiki' olive trees, increased oil yield, peroxide content, and antioxidant capacity. The results of these works contribute to the recommendation of fertilization programs in olive trees, especially in the growth and productive phase of the crop, in addition to directions for further research.