Olive tree growers have a vested interest in making sure that their olive trees maintain a high level of good health. To this end, they need to make sure that the orchard is adequately irrigated. Olive trees that get the water that they need produce consistently superior growth, larger fruits, better yields at harvest, and annual bearing. This is in contrast to trees that are water starved or stressed.
Olive trees are a hardy species that can grow in relatively arid regions. This is because the leaves of the tree are relatively small and hairy, and this feature slows down the rate of transpiration, or water loss. This survival mechanism is a good thing overall, but can be expensive in terms of oil output if it is not kept in proper balance.
Because of this, olive oil yield is somewhat a function of how much water the trees get, with the potentially largest yields available the more water is added. At the same time, care needs to be taken that the humidity of the soil does not become oppressive.
Due to considerations like these, potential grove sites need to be put through their due diligence. This means that they need to be carefully studied to ensure that there is enough irrigation water on hand to make the endeavor financially competitive, but not too much to damage the trees.
This is by no means an easy project. On the contrary, this kind of irrigation planning involves complex operations of different kinds. There will have to be calculations made with reference to pressurizing mains, the size of pumps, the size of mains, pressure reduction, and making allowances for terrain conditions. Care must be taken to make sure that these calculations are spot on, in order to avoid the costly waste of valuable resources.
Installing an irrigation system will be most necessary in cases where:
* The natural rainfall in the region is not adequate.
* When there is sufficient humidity only during the winter months, leaving the soil relatively dry during the spring.
* When the soil is rocky or sandy, and does not have the capability of effectively retaining moisture.
Orchard planners need to know the minimum amount of water that will be needed to irrigate each acre during sunny, dryish weather. That amount is generally agreed to be about 7,000 gallons per acre each day, which breaks down to about 5 gallons per minute. It should be noted that cooler coastal areas may need less than this, and drier inland regions somewhat more.
Care needs to be taken to ensure that the young trees get the best start possible. To achieve this, they should never be allowed to go dry, and therefore should be constantly irrigated. In many cases this will mean making use of a drip irrigation system.
The irrigation infrastructure should always be put in place before the grove is planted. Which system to select will depend on cost, the kind of terrain to be irrigated, ease of maintenance, as well as the availability and cost of water.
Low volume irrigation systems such as drips, mister/foggers, mini-sprinklers, and fan jet systems tend to be slightly more expensive, but are highly efficient and can be used on sloping terrain. They apply precise amounts of water to areas around the trees, and are useful in situations where the terrain cannot be reasonable leveled out.
Sprinkler systems apply more water that low volume systems, and thus are more useful in situations where runoff is minimal. They can be permanently fixed into place in the grove, or mounted on mobile hoses or pipelines. It should be noted that mobile systems are usually less expensive initially, but are labor intensive to operate.
Pipeline and open ditch systems are the cheapest of all, but are usually only useful if there is abundant water available and if the cultivation area is relatively flat. Whichever system is eventually settled upon, it should always be installed prior to pre-plant fumigation.
There will be some variation in the layout of different systems, but the key considerations remain the same in each case. These are whether the system is mobile or not, whether it is drip or spray, where pressurization and water sources are, and whether or not any automated controllers will be used. The main thrust will be to minimize the amount of mainline and wiring that will be necessary.
Planners need to keep in mind that there will be constant traffic in the orchard. Because of this, in the case of movable of drip irrigation they should make sure that the stub ups are out of the way, and tubing runs are unobtrusive. In the case of spray irrigation, the heads will need to be protected from accidental impacts.
Once the overall plan has been decided, measurements can be taken, supplies procured, and the construction process commenced.