Study on the Use of Biostimulants in High-density Olive Growing: Quality and Production

Due to the increase of high-density holdings, especially of olive trees, the nutritional requirements of the plants are higher per unit area, which implies that a greater contribution of fertilizers to the soil is needed. Opting for fertilizers of inorganic origin will produce an increase in the pollution of the soil. There is a clear tendency nowadays towards the use of environmentally friendly cropping techniques, there is a special interest in the practice of organic fertilization with products coming from extracts of algae and/or crops, which provide a high organic matter content that delivers the necessary nutrients to the plant. In the face of this possible soil contamination, our aim is to analyze the effect of biostimulants as an alternative to chemical fertilizers, to steadily produce and maintain high quality standards during the life of the crop. Our objective is using more environmentally friendly products in order to satisfy one of the most important demands from both consumers and the authorities. In this study, we carried out five different treatments in addition to a control treatment with a supply of NPK, from inorganic products, which are used to control fertilization with a solution obtained from seaweed extracts. These treatments were applied in two crop cycles for two of the most important varieties in the current olive tree growing scenario: Arbequina and Koroneiki. This study was developed in the farm Pozohondo, which is located in a crop zone by the Palancia river (Castellon, Valencia, Spain), in the southeast of the Iberian Peninsula, where the olive trees were established in a high-density system with a planting framework of 4 x 1.5 m. We ensured an exhaustive control of the nutritional needs of the holding by using a fertigation system. We could notice differences in the productions of each applied treatment, avoiding any possible biases through the additional control of 100 randomly selected olives from each of the samples. There is an improvement in the set of physical characteristics of the olives with the treatment that provides amino acids and extra potassium based on amino acids. We analyzed the quality of the olive oil obtained from the production of each treatment by measuring the fatty acids, tocopherols and polyphenols contents. We also carried out an organoleptic tasting analysis following the rules of the International Olive Committee (IOC). We observed an improvement with regard to the rest of treatments in the pomological parameters of the olives when applying the potassium and amino acid biostimulant, while the quality of the soils was not affected by the type of fertilization applied in each treatment. We achieved an improvement in production by making different extra biostimulant contributions, which can be said to replace, at least under our working conditions, fertilizers of an inorganic origin.