Soil Management Practices, Fertilization, Pruning, and Harvesting of Olive Groves in Tunisia

In Tunisia, oleiculture represents one of the principal economical and agricultural strategic sectors. In fact, about 80 million olive trees are spread over 1.8 million hectares. More than 97% of this area is conducted under dry farming system. Dry-farmed olive orchards of arid and semiarid areas are traditionally widely spaced to take full advantage of the stored water from winter rains for spring and summer growth. Additionally, soils of Tunisian olive orchards have low water holding capacity and low soil fertility are and are exposed during the dry season to long periods of soil water deficit, coinciding with the active fruit growth and oil synthesis. In the Tunisian low-density olive orchards, mechanical tillage still represents the most common technique of soil management. In the north, soil tillage is limited to two interventions per year using disc plow, while in the center and south, the soil was mechanically tilled 3–4 times per year at a depth of 0.15–0.25 m and perpendicular to the slope using a cultivator with dovetail. In rainfed olive grove farm, manure is the most organic amendment used by farmers to improve olive grove nutrition (Haifa Group, 2013). But during the last decade, the use of olive mill wastewater as an organic amendment is widely recommended and applied every 2/3 years at the rate 50m3.ha−1. A few farmers used green manure, especially leguminous mainly in the northern areas in which rains exceeds 400 mm/year. Pruning is necessary to adjust the trees to the climatic conditions of the area and increase the productivity of a plantation. The aims of pruning are (1) to balance vegetation with fruit yield, (2) to minimize the nonproductive period, (3) to prolong the productivity of the trees, (4) to delay senescence, and (5) to save soil water, a critical factor in nonirrigated orchards. The most applied pruning types: In the irrigated olive orchards, short pruning shape used is, namely, the “short cup.” In the former shape, branching takes place very close to the ground, at a height of 40–60 cm, while in the latter no pruning is done in the first 3 years. Afterward, only weak shoots and top branches are removed. For table olives, Meski and Picholine are the main table olive cultivars used. Fruits that are to be processed as green olives are picked while they are still green but have reached full size, generally early in October. Ripe olives bruise easily and are harvested by handling with care. For oil olives, harvesting start at the second week of November, and the most methods used include manual harvesting, such as small hand rakes, picking bags with a harness, and pneumatic olive harvesters.