EFFECT OF THE CLIMATE AND THE SOIL CONDITIONS ON CROPS PERFORMANCE OF THE "CHEMLALI DE SFAX" OLIVE TREES

In spite of the climatic aridity characterized by the weakness of the precipitation (annual average of 200 mm) and its irregularity throughout the seasons, the olive groves of the south insure 60 % of the Tunisian oil production. In those rainfall conditions, tree development and yield vary considerably and depend hugely on the soil quality. Olive crops evolvement during 60 years in three 80-year-old orchards shows that, the yield of the year (n) depend on rainfall of the same year and the year before (n-1). For olive trees planted on deep sandy soil, the yields reach 65 kg / year / tree and the alternate bearing is weak. But on clayey - loamy - sandy soil and often shallow (depth less than 0.8 m), annual production didn't exceed 14 kg per tree and per year and the alternate bearing is frequent. Furthermore, our results show that the olive tree vegetative growth, flowering and fructification were in relation with the soil structure.