Olive (Olea europacal) probably originated from the Eastern Mediterranean region of the Middle East. Present production is about 16 million tons green and black table olives and 2.7 million tons oil. Of the total production, 95 percent is produced in the Mediterranean region with Spain and Italy being the main producing countries FAOSTAT, 2001) .
The crop is indigenous to the Mediterranean region with a mild, rainy winter and a hot, dry summer. A dormancy period of about two months with average temperatures lower than 10° C is conducive to flower bud differentiation. Some cultivars are adapted to areas with higher winter temperatures but reduced flowering is noted under these conditions. During the dormancy period, the tree tolerates short periods of frost of -6° C, but during the bearing period frost causes damage to the fruits which are then only suitable for oil production. High temperatures and dry winds cause poor fruit setting and excessive drop of young fruits with remaining fruits shrivelling on the tree. A long, sunny, warm summer results in a high oil content of the fruit. High humidity at f lowering causes flower drop and infestation of sooty mould.
The crop produces acceptable yields on poor soil as long as it is deep, well-aerated and free from waterlogging. Under waterlogged conditions damage through lack of oxygen and fungal diseases increases sharply. The fertilizer requirements are 200 to 250 kg/ha N, 55 to 70 kg/ha P and 160 to 210 kg/ha K. Nitrogen is applied prior to or during the flowering and fruit formation period.
The olive tree is moderately tolerant to soil salinity provided ECe does not exceed 8 mmhos/cm, but ECe of 4.5 mhos/cm or less is preferred.
Raised for two years in the nursery, the tree is transplanted early in the season with 15 to 20 trees/ha under poor rainfed conditions and up to 300 trees/ha under irrigated conditions. Tree density is also dependent on the method of pruning. Early pruning is not essential but is often practised to obtain strong stems. However, for older trees, pruning during winter is necessary for high yields. Intercropping with grain forage and vegetable crops is sometimes practised in young orchards but is discontinued after 15 to 20 years under rainfed and after 6 years under irrigation.
More fruits are set than can be supported by sufficient nutrient supply, and this tendency increases as the trees get older. Consequently, a small number of flowers produce fruits. Early flower drop can be attributed to inadequate pollination, nutrient deficiencies or water shortage. Late flower and fruit drop is caused mainly by olive moth and olive fly attacks and water shortage. On the other hand, abundant fruiting adversely affects growth of annual shoots and the next year crop and eventually leads to alternate fruit bearing. This tendency is greater in older trees but alternate bearing is less pronounced with good soil and climate, and adequate management practices. The economic life of a tree is 50 years under rainfed conditions but under favourable growing conditions it can be much longer. A profitable harvest is obtained after 6 years but under more extreme conditions, after 15 to 20 years.
The graph below depicts the crop stages of olive, and the table summarises the main crop coefficients used for water management.