The olive tree, Olea Europea, has always mistakenly been considered a crop which requires little water, and irrigation has been reserved for table olives. Today almost all intensive and traditional olive cultivation uses irrigation, obtaining the following results:
- Rapid development of foliage in the the early years of planting;
- Earlier onset of fruit production;
- Increased yield and quality;
- Reduced problems of alternate bearing.
The species needs high levels of sunlight, low atmospheric humidity, variable temperatures and well-drained semi-clay soil with adequate aeration for root growth. The root system is superficial, but can develop roots which may spread a considerable distance from the trunk. This species has morphological, anatomical and physiological properties which enable it to survive in drought conditions. On average, an adult olive tree in good health needs between 1 and 1.2 litres of water per square metre of foliage per day.
To calculate the volume of irrigation water needed, a crop coefficient of 0.5 – 0.7 should be taken into account; this may rise to 1.0 in plantations with weeds or in hot, arid areas. Average water consumption is around 2000 – 2500 cu.m./ha./year.
Irrigation plays an even more important role in modern super-intensive olive growing, which sees 1600 to 1900 trees per hectare, with the resulting increase in water requirements.
For this crop again, micro irrigation is the most efficient method from the agronomy point of view, and the most economically sound. The use of drippers such as Mono®, Tandem®, Junior® and Multibar® allows water and nutrients in solution to be delivered to the optimal point of the root system. The flow rate of the drippers varies from 1.6 to 3.8 litres/hour and is chosen according to planting density, soil type, quality of water source and type of olive tree. In intensive plantations with layout of 5 x 5 or 5 x 6 m, it is advisable to use one or two driplines per row, with drippers between 60 and 125 cm apart, while for super intensive olive groves with spacing of 3.5 x 1.5 m, the interval should be 50 cm in order to create a continual watered strip and encourage the development of plants with much smaller root systems. In traditional olive groves with lower planting density, a suitable number of inline drippers such as the iDrop® can be used to avoid wasting water between trees; these have a flow rate up to 8 litres/hour.
The driplines can be suspended from supporting wires or laid on the ground. An irrigation method which is gaining popularity for olive growing is subirrigation, where one or two driplines per row are placed under the soil. The advantages of burying the lines are clear:
- Water saving due to lack of evaporation;
- Facilitates fertigation;
- No obstruction to machinery used for pruning and harvest;
- Longer working life for the irrigation system;
- Improved appearance for the olive grove.
Irritec driplines for subirrigation are fitted with ROOTGUARD® protection, which protects the drippers from penetration by roots. The system is installed by machine, using appropriate equipment which makes the work faster and less expensive. In traditional olive groves, subirrigation eliminates the cost of suspended wires and supporting poles.