Olives have been cultivated for at least 5,000 years—for their oil and their fruit. Yet, all this time, the olive tree itself was a stingy, hostile, uncooperative friend to man. The yield per tree was always miserably low, with less than 2% of flowers becoming mature olives, and sometimes ending in total failure. They were very difficult to propagate; young trees became old before their time, and then lived on, not quite sterile, for hundreds of years (up to 700, it is believed). A most unsatisfactory agricultural species.
In our own period, as excellent alternative oils were developed, olive growing became increasingly uneconomic. Production declined, prices went up, consumption declined, and the industry became poorer and poorer. Some growers switched to other crops, yet large areas of
Spain, Italy, and Greece—collectively responsible for at least 70% of the world’s olive oil production, and more suited to olive-growing than anything else—seemed doomed to economic extinction. Then, a revolution began—
la olivicultura moderna.
Olives and the EU
The agent of change was a curious alliance between agricultural science and the European Union (EU). Since Spain and Greece joined the European Community in 1986, olive revenues to farmers have more than doubled, thanks to a system of subsidy and price guarantee under the Common Agricultural Policy.
As production increased, prices to the consumer lowered. The industry has been saved. In Spain, there are special schemes to encourage new plantations, and cereals are being replaced by olives in the field.
Adapting olive culture
On the olive culture side, perennial problems are at last being solved or circumvented. Out of 500 varietal types, 24 have been identified as having superior characteristics for:
- Propagation
- Yield
- Quality
- Resistance to fruit-drop
New methods of multiplication, particularly in vivo rooting under mist irrigation, have greatly improved the availability of healthy young trees, particularly in Spain. These trees now come into production in as little as three years, as opposed to an average wait of 15 years before the olive revolution. The new olives are single-stemmed, and therefore appropriate for mechanical harvesting.
Increases in productivity are being brought about by higher tree densities in the new Spanish plantations. Traditional densities were 80 to 100 trees per hectare; densities of 200 and more are now possible. At present, this tends to reduce the yield per tree, but the overall yield per hectare is up by about 40%.
Boron for plant nutrition
On the agrochemical side, startling advances are being made in pest control and plant nutrition. Historically, olives have received little or no remedial care, bar occasional pruning and removal of dead wood. Now they often receive three or four treatments per year, and pests such as the olive fly and the olive moth are being eliminated.
In Spain, nothing has made more difference than the application of
boro (boron). Olives typically are grown on calcareous soils which prevent or impede absorption of the boron in which they are naturally low. This, plus the extremely dry conditions which occur every year (particularly in southern Spain) result in the boron deficiency which we now know, has had much to do with poor yields and sick trees.
For centuries, the trees themselves have been trying to tell their cultivators about boron deficiency through:
- Discolored leaves at the tips
- Prematurely shedding leaves
- Branches dying back
- Producing a multitude of barren suckers
- Deformed or corky fruit that fall to the ground unusable
Boron’s essentiality to plant life has been accepted for more than 80 years, and the relatively high requirements of certain species such as apple, grape, and olive are well documented. Yet, until the changes brought about by the EU’s agricultural policies, olive growers—many of them little more than subsistence farmers—seldom achieved returns which could justify or even allow investment in plant nutrition, as recommended by agronomists. Olives had never received boron supplementation in the past—what proof was there that it would work, and where would the money come from?
There is now abundant proof that the age-old problems of fruit set, fertilization, die-back, sterile suckers, fruit drop, and deformed corky olives are significantly due to boron deficiency. It has been shown that very small amounts of borate fertilizer, foliar application of 20 to 30 grams per tree, for example, can double or triple yields, even from old notoriously infertile trees. The effect is a rejuvenation. The cost of the boron—U.S. Borax’s
Solubor fertilizer being the most convenient source of
boro for calcareous soils—is repaid tenfold or more by increased yields of better quality olives.
With the application of
boro now economically feasible for all growers, the future for those still unregenerated trees can be as golden as the best extra virgin olive oil itself.
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