Efficiency of foliar fertilization for the improvement of pomological parameters, mineral composition, carbohydrates status and polyphenols components in olive fruit cultivar Chemlali

Abstract

Foliar fertilization in rain-fed olive orchards is used nowadays in order to improve the yields for the olive oil industry. The present work aimed to study the effect of foliar fertilization on the quality parameters of olive fruits. Three foliar fertilizers and biostimulants were applied on Chemlali olive cultivar, cultivated under rain-fed conditions in the center of Tunisia, at different stages from the vegetative cycle during two successive years. Six treatments formed the fertilization program: F1 (rich in nitrogen), F2 (rich in boron), F4 (a biostimulant rich in calcium), F3 (supplying an addition of F1 and F2), F5 (supplying an addition of F1, F2 and F4) and a control (without foliar fertilization). At the end of the experiment during the year 2015, fruits were harvested, freeze-dried and the characteristics of drupes and chemical composition of the fruits were evaluated: mineral composition, carbohydrates profile and individual polyphenols. Results showed that some treatments especially rich in Ca improved the fruit size. Foliar fertilization induced differences in the mineral content of fruits. Regarding carbohydrates, glucose was the main sugar present in the fruits and varied between 8.8 μg/mg dry weight (d.w) and 36.43 μg/mg (d.w.). Changes were clearly observed in the pool of the phenolic fraction. The combined treatment F5 showed the highest concentrations in oleuropein and hydroxytyrosol and were equal to 742.6 and 112.94 μg/g of fresh weight respectively. This work is of great interest because it showed the role of nutrients supply in improving the quality of olive fruits.

Keywords:

• Olive fruit
• foliar fertilization
• fruit characteristics
• mineral elements
• phenolic compounds
• soluble carbohydrates

Acknowledgments

We are grateful the members of the Olive Tree Institute (Sousse, Tunisia), for the team Biochemical Laboratory, USCR Mass Spectrometry, LAB-NAFS/LR12ES0500 Nutrition-Functional Foods and Vascular Health in the faculty of medicine (University of Monastir). Our special thanks go also to the members of Laboratory of soil testing and plant analysis in the Instituto Superior de Agronomia (University of Lisbon) for their help and assistance to carry out some analysis.

Disclosure statement

No potential conflict of interest was reported by the authors

Additional information

Funding

This study was supported by the Ministry of Higher Education and Scientific Research in Tunisia.