The quality of olive oil is determined by a combination of chemical, physical, and sensory properties. In extra virgin olive oil, it is essential that the content of free fatty acids does not exceed 0.8 g per 100 g of oil and that it possesses appropriate sensory properties. Numerous factors influence the quality of olive oil, including excessive nitrogen fertilization. Higher nitrogen content in the fruits leads to a lower content of phenols and oleic acid, which results in poorer oxidative stability, pungency, and bitterness. With increasing nitrogen content in the fruits, the content of linoleic acid, linolenic acid and free fatty acids increases. According to the literature nitrogen application through an irrigation system had a similar effect on olive growth and olive oil quality as direct nitrogen application to the soil. Additional foliar nitrogen fertilization during the period of intensive oil accumulation in the fruits did not adversely affect olive oil quality. Further research is needed to determine nitrogen requirements more precisely. The optimal nitrogen rate differs among olive orchards. The rate and form of applied nitrogen should be adjusted according to plant nutritional status, growing conditions and the production system.
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