**4. Conclusions**

Results show that the organic practices in unirrigated orchards had a noticeable yet commercially modest effect on the chemical and physical-chemical parameters and the volatile compound profile. The effect was much less strong than that of the harvesting method, which affected severely the chemical and physical-chemical parameters, including the quality parameters (which are used in the official oil grading), and the volatile compounds. Conversely, the harvesting time in real conditions was revealed to be a factor with little repercussion on the oil quality parameters, which might be due to a suitable harvesting time schedule, although it had a noticeable effect on some important volatile compounds. Previous studies have not shown a consistent effect of the organic production on the olive oil characteristics, partly because of the difficulty of controlling other sources of variation. Our results, for oil obtained in a commercial mill, reveal an increase in the total phenols in the organic oil, which was previously reported at laboratory scale and attributed to the decreased availability of nitrogen due to the lack of chemical fertilisation. This result, obtained under controlled conditions (e.g., the same mill, the same area, the same harvesting time and method) could explain the increase in oil stability and the changes in the volatile compound profile. Considering that some studies involving irrigated orchards have not shown an increase in phenols, it would be advisable to perform further studies

under controlled conditions to shed light on how irrigation may affect the effect of the organic practices, and on whether or not the organic fertilisation currently used in commercially exploited orchards causes a consistent decrease in soil nitrogen availability. That information would help understand the real defect of the organic production and how to deal with it.

**Author Contributions:** Conceptualization and methodology, A.I.C., J.S.-C., L.M. and C.d.M.; formal analysis, A.I.C.; investigation, A.I.C., A.R., J.S.-C. and M.M.-C.; resources, A.I.C., J.S.-C. and L.M.; writing—original draft preparation, A.I.C. and A.R.; writing—review and editing, A.I.C., L.M., J.S.-C., M.M.-C. and C.d.M.; supervision and project administration, A.I.C., J.S.-C. and C.d.M.; funding acquisition, A.I.C., J.S.-C. and L.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was partially funded by Junta de Extremadura and FEDER, project GR18147.

**Conflicts of Interest:** The authors declare no conflict of interest.
