Olive (Olea europaea L.) Tree Nitrogen Status Is a Key Factor for Olive Oil Quality

Abstract

The influence of macronutrient status on olive oil properties was studied for three years. Data were analyzed by a multivariate model considering N, P, K, and fruiting year as explanatory factors. Oil quality parameters were primarily associated with N concentration in leaves and fruits which increased with N in irrigation solution. The effect of P on oil quality was mainly indirect since increased P availability increased N accumulation. The potassium level had negligible effects. The oil phenolic content decreased linearly as a function of increased leaf N, indicating protein-phenol competition in leaves. The overall saturation level of the fatty acids decreased with fruit N, resulting in increased polyunsaturated fatty acids. Free fatty acids increased with increased levels of fruit N. High fruit load tended to reduce fruit N and subsequently improve oil quality. The effect of N on oil properties depended solely on its concentration in leaves or fruits, regardless of the cause.

Mycorrhizal, nutritional and virgin olive oil parameters affected by groundcovers

“…Our results indicate that olive nutritional status and harvest parameters are important for oil quality in agreement with Erel et al. (). Olive trees with heavy loads slow down the ripening process ( Trentacoste et al., ).…”

Effects of nitrogen fertilization and nitrification inhibitor product on vegetative growth, production and oil quality in ‘Arbequina’ hedgerow and ‘Picual’ vase-trained orchards

“…Meanwhile in other experiments, a reduction in linoleic acid coincided with N-application, and, consequently, a decrease in the relation between UNFA and SAFA was observed (Toplu et al, 2009). Erel et al (2013) reported that the level of desaturation for the three major C18 fatty acids (oleic, linoleic and linolenic acids) increased with fruit N-content. However, these authors pointed out that no solid linkage between N and oleatedesaturase could be found in the literature and the N-level may indirectly affect desaturation via assimilate availability.…”

“…Under high N conditions, the synthesis of proteins demands a high amount of the precursor, reducing the synthesis of phenols and hence polyphenols. In olives it has been observed by Erel et al (2013) that fruit phenol content is inversely related with N in leaf, and they suggested that either phenol precursors or polyphenols themselves could be produced in leaves and translocated to the fruit, and it is on the leaves where the competition between both pathways occurred. These authors obtained a negative relationship between high nutritional N-doses and oil quality in olive trees, and observed that when N content in leaves increased, oleic acid and polyphenol content were reduced, negatively affecting oil quality.…”

“…Therefore, an excess of N-fertilization could cause nitrate pollution and increase frost and disease sensibility. Moreover, it could negatively affect oil quality (Fernández-Escobar et al, 2006) because of a decrease in polyphenols, which are the main antioxidants (Erel et al,2013). Fernández-Escobar et al (2009) fertilized the soil and foliar parts with N, applying different doses of N when the previous season's N-leaf concentration was below the threshold limit for deficiency.…”

Effects of reclaimed wastewater irrigation and fertigation level on olive oil composition and quality

“…Irrigation with RWW, while using routine fertilization regimes not considering nutrients delivered with the water, might expose plants to excess levels of the macronutrients N, P and K . Previous works showed that olive oil composition and quality are remarkably affected by the amounts of N and P, while K has a minor effect . Total phenolics content (TPC) decreased in response to fertilization with high levels of N .…”