Optimal Time of Supplemental Irrigation during Fruit Development of Rainfed Olive Tree (Olea europaea, cv. Picholine marocaine) in Morocco

Aims: This work was carried out to identify the optimal time of supplemental irrigation on a traditional rainfed olive orchard. Study Design: Randomized complete block design with three replications where the variable factor was water regime. Place and Duration of Study: Experimental station AinTaoujdate, Regional Agricultural Research Center, Meknès, Morocco during 2009 and 2010. Methodology: Seven treatments of supplemental irrigation were tested, individually during one day at, beginning of stage I of fruit development (Ta); beginning of stage II (Tb); beginning of stage III (Tc) and in combination of two irrigations, Ta and Tb (Tab), Ta and Tc (Tac), and Tb and Tc (Tbc) in addition to three irrigations Ta, Tb and Tc (Tabc), and no irrigation used as control (Td). Treatments were applied to thirty years old olive trees (cv. Picholine Marocaine) planted at a distance of 8x6 m, at experimental field of Regional Agricultural Research Center of Meknes in North-center of Morocco. Amount of each watering was equivalent to the easily usable water-reserve on 70 cm of soil depth (0.5 m3/tree). Results and Discussion: Fruit weight and shoot length were more affected by treatment Ta as compared to the rainfed regime, and hence fruit and oil yields were increased, in average, respectively by 43% and 37%. Water use efficiency for this treatment was 23 kg.m-3.tree-1. Treatments Tb and Tc improved only oil content and shoot growth without significant changes in yield. However, their combination with Ta (Tabc) increased fruit yield by an average of 106%. The effect observed under the tested irrigations was related to the importance of fruit growth kinetics during water application. Conclusion: The production gain of supplemental irrigation, applied particularly during the first period of fruit development, is promising to promote this technique on several rainfed olive orchards