**2. Assessment of soil fertility and nutritional status in olive orchards**

We proceeded with a diagnostic study of soil fertility and olive tree nutritional status in 58 orchards chosen at random in Central Morocco. This study was carried out through soil analysis, surveys, and leaf analysis. Composite soil samples were, therefore, taken from the two layers of 0–30 and 30–60 cm during the period of vegetative rest of the crop, which is December–January. Leaf samples were also taken during the same period and from the same olive orchards.

## **2.1 Description of studied olive orchards**

Through the surveys carried out, we have observed that the Moroccan Picholine variety dominates (98.3%) in olive orchards and that the olive tree is associated with intercropping in almost half (48.3%) of the orchards studied. The chosen sample is characterized by different age categories ranging from 4 years to over 70 years. Orchards belonging to the age group between 11 and 40 years old represented 60% of all the olive groves surveyed, while young orchards whose age does not exceed 10 years represented only 5%. More than half (57%) of the orchards studied are managed in rainy conditions. In irrigated orchards, the gravity irrigation system dominates with a proportion of 24% against 19% of all orchards surveyed for the drip irrigation system. The majority of plantations (85%) have a planting density between 100 and 350 trees.ha−1. We noted that about 30% of the orchards studied have a planting density between 200 and 350 trees.ha−1. This is the optimal density recommended for the Moroccan Picholine variety in the study area. However, the study showed lower densities ranging from 100 to 200 trees.ha−1 at 55% of the olive groves studied. The yields declared by the olive growers surveyed varied greatly from one farm to another. They varied between 0 and 14.3 T.ha−1. The average olive yield was higher (5.1 T.ha−1) in olive trees under drip irrigation system, compared to those under gravity irrigation system (1.9 T.ha−1) and in rainy conditions (1.8 T.ha−1). Olive orchards whose planting density belongs to the density class [200–350] trees.ha−1, which represents the optimum planting density for the Moroccan variety Picholine at the regional level, achieved the best average olive yield (3.7 T.ha−1), in comparison with the other density classes identified. On the other hand, the extensive densities (<100 trees.ha−1) allowed the minimum average yield (1.5 T.ha−1).

### **2.2 Fertilization practices adopted by olive growers**

About 48% of the olive growers surveyed do not use any mineral fertilizers for their olive trees. The absence of fertilization had repercussions of course on the olive yield that was on average 3 T.ha−1 in the fertilized orchards against 1.9 T.ha−1 achieved in the unfertilized olive orchards (**Table 1**).

The calculation of the average doses of nitrogen, phosphorus, and potassium in the orchards studied showed that nitrogen (N) is the most provided element by farmers with an average dose of 37 Kg N.ha−1, followed by phosphorus (P) with 20 Kg P2O5.ha−1 and finally by potassium (K) with 9 Kg K2O.ha−1 (**Table 2**).

If we consider the most abundant density in our sample, which is 100 trees. ha−1 (42.4% of orchards), these average doses applied become as follows—0.37 Kg N.tree−1, 0.2 Kg P2O5.tree−1, and 0.09 Kg K2O.tree−1. And these are low doses for the olive tree. In addition, phosphorus is supplied by some farmers at very high doses that even exceed nitrogen and that have reached 138 Kg P2O5.ha−1. The times of fertilizer input were generally concentrated over the period from January to April indicating an absence of inputs during other periods where the need for mineral elements is important for the olive tree, such as the fruit growth phase.

Finally, all these data indicate the existence of a failure in the fertilization practices adopted by the olive growers surveyed concerning both the fertilizer doses applied and their application moments.


#### **Table 1.**

*Average olive yields.*


#### **Table 2.**

*The nitrogen, phosphorus, and potassium quantities provided by olive growers surveyed.*
