**4. Conclusion**

The results of the diagnostic study showed that fertilization is not well controlled by olive growers and olive orchards are not well nourished with essential elements for their production. This was confirmed by soil and leaf analyzes of samples taken from these orchards. Hence need to study the impact of this technique on olive production by conducting field fertilization trials, especially since in Morocco few studies have focused on this aspect.

The results of the olive tree fertilization trials conducted in different regions showed that nitrogen did not improve olive tree productivity parameters in two sites and even negatively affected the olive oil quality. At S2, nitrogen improved yield, yield efficiency, and olive oil content; the best results were obtained with the dose of 0.5 Kg N.tree−1.year−1. Phosphorus did not have a significant impact on the olive tree at the three sites. Potassium affected yield and yield efficiency at one site (S3) and had no effect on oil content and quality. An application of 0.5 Kg K2O.tree−1.year−1 allowed a good yield.

The results of three experimentations showed that the effect of mineral fertilization on the olive tree was variable depending on the environment where it is grown (climate and soil of the site), the variety, and the orchard age. The fertilizer input is conditioned by the combination of all these parameters. The results of these field trials remain preliminary given the short duration of experiments. Field trials on olive fertilization should be repeated for several years and in different agro-climatic zones to be able to emerge reliable standards of crop fertilization. However, from this work, it can be concluded that nitrogen and potassium are the two most important elements for olive nutrition and which can affect both its productivity and its quality. The impact of phosphorus on the crop has not been significant, whereas our farmers provide it in high doses compared to the crop's need.

In Morocco, fertilization standards for the olive tree are not yet clearly defined. Research work on this topic seems to be insufficient and should be further developed.
