EFFECT OF IRRIGATION FREQUENCY ON THE YIELD AND VEGETATIVE GROWTH OF TWO OLIVE CULTIVARS (CVS . KORONEIKI AND PICHOLINE) I N ARID LANDS - A. Sghaier; R. B. Ayed; N. Sghaier; K. Naggaz; M. Ouessar; D. Boujnah (Journal of Animal and Plant Sciences, 2019)