The olive leaves are known as a source of nutraceuticals due to their richness in phenolics. Numerous studies explored the effect of several factors on leaf phenolics but few studies focused on the impact of foliar fertilizers on leaf phenolics. In this context, our study aimed to explore the effect of season and foliar fertilisers on phenolics in leaves of “Chemlali” olive cultivar. Four foliar fertilisers were sprayed separately at different seasons. Total polyphenol, total flavonoid ortho-diphenol and oleuropein contents were assessed in fresh olive leaves.

Our results showed that polyphenols and ortho-diphenols reached their maximum in April, decreased in August and rose again in November. Flavonoid showed an inverted trend and were the most affected by the different foliar fertilisers. Oleuropein content had two peaks in April and November and was not affected by foliar fertilisers.

Taking into consideration these results, the optimal periods to collect olive leaves are April and November. Our study brought out evidences about the impact of foliar nutrition on olive leaves.