## 5 Conclusions  
This study has shown that foliar application of bio-stimulants, such as silicon (Si), can affect olive fruit morphology, olive oil production and quality parameters, fatty acid composition and phenolic content to some extent. Fruit and stone morphological parameters were most affected. As well as large differences between the two studied cultivars, increases were evident with increasing Si foliar application, especially in fruit and stone length and width as well as pulp mass, while pulp percentage did not change. Olive yield per tree was increased by Si2 treatment (1.1 g Si/L) only for the Leccino cultivar, suggesting that a higher total olive oil yield per tree is related to specific cultivar x treatment interplay. Olive oil quality parameters, also mainly predefined by the cultivar, were within the limits for EVOO prescribed by the regulation in force and were not compromised by Si treatments. The results obtained show that foliar application of Si can affect the proportions of some fatty acids (16.0, 16.1, 17.1, 22:1), but the effect of genotype was again generally much larger than that of the applied Si treatments. Sporadically irregular effects of Si on some minor phenols (apigenin, the sum of flavonoids and the sum of phenolic acids) were observed, in all cases expressed for one cultivar and not for the other, which was also evident in the form of significant interactions between cultivar and treatment. Further research should investigate how Si foliar application affects other cultivars, as well as the seasonal variability of these effects. Improving product quality while attaining higher yields would be a milestone inany form of plant production, so the observed increase in olive yield per tree after Si foliar treatment also deserves further attention.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app142411500/s1](https://www.mdpi.com/article/10.3390/app142411500/s1)]([https://www.mdpi.com/article/10.3390/app142411500/s1](https://www.mdpi.com/article/10.3390/app142411500/s1)). Figure S1. Differences between cultivars (IB, LE) for oleic to linoleic (O/L, A) and palmitic to linoleic (P/L, B) ratios. Figure S2. Multiple comparisons of the effects of treatment (Si1, Si2, Si3) and cultivar (IB, L) on peroxide value (PV, measured as eq O2/kg) of olive oil from IB and L cultivars.  
Conceptualization I.P. and S.G.B.; validation and formal analysis M.L., S.M., S.R., I.N., U.K., B.S. and M.P.P.; investigation I.P., S.M. and M.P.P.; resources I.P., S.G.B. and M.L. data curation M.F. and I.P.; writing--original draft preparation M.F., I.P. and M.L. writing--review and editing M.F., I.P., S.G.B., S.M., M.L., S.R., I.N., U.K., B.S. and M.P.P.; visualization M.F. and M.P.P.; supervision I.P. and S.G.B.; project administration I.P. and M.P.P.; funding acquisition I.P. and S.G.B. All authors have read and agreed to the published version of the manuscript.  
Open access publication costs for this research was financed by EARDF (European Agricultural Fund for Regional Development), in a framework of Intervention 70.05. Support for the preservation, sustainable use and development of natural resources in agriculture from the Strategic Plan of the Joint Agricultural Policy of the Republic of Croatia 2023-2027 (No.: 950-05-/24-70-05/0005).  
Not applicable.  
The data supporting our findings and analyses are contained in the article itself. Readers can access this data by referring to the article.  
The authors declare no conflicts of interest.