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Olive growing and production in arid conditions

In a lot of countries, the most important production factor is plantation density. Interesting the possibility to develop a deficit irrigation model to save water

In Tunisia the study of the production and the vigour parameters for 18 years show high potential of production according the density of plantation that varies between 51 and 156 trees/ha against 31 trees/ha in traditional plantations.
From the fourteenth year of plantation the researchers found a decrease of the production by tree and a reduction of the vigour caused by competition.
The biological and physiological measures reveal an entanglement of the roots for the most elevated densities of plantation. The effect of this density on frutification is only marked at an advanced development stage of the fructiferous organ.

So, in arid countries it is very difficult to increase the plantation density but it is possible, also if the water resources are very poor, if farmers adopt correct agronomic techniques, as irrigation in deficit.

In a climatic pattern of sub humid zone, characterized by precipitation during spring months, scarce or no rainfall from mild June to August, is sure indicated for a deficit irrigation scheduling strategy.

In an scientific experience for four seasons in the San Joaquin Valley of California three regulated deficit irrigation (RDI) treatments were imposed on mature olive trees (Olea europea cv. Manzanillo).
The RDI regimes imposed deficit irrigation generally during June and July. Drip irrigation was used on trees with a spacing of 4.57 x 9.14 m. The RDI regimes resulted in mean seasonal applied water of 645, 579, and 432 mm per season; reductions of 16.2, 24.8, and 43.9% from the 770 mm for the Control (determined using previously established crop coefficients and real-time reference crop water use).
Results to date suggest that the RDI regime that saves about 25% (200 mm) of full ETc may be useful in conserving water while maintaining top yields of high quality fruit.

A similar experiment was maked in Spain: four irrigation treatments were applied during 1996 in a commercial olive plot (Olea europaea L. cv. “Arbequina”).
The Control treatment was irrigated at 100% Etc (estimated crop evapotranspiration) during the whole season. Additionally three RDI (regulated deficitary irrigation) treatments were applied between the beginning of massive pit hardening (5 July for 1996 season) and the third week of September, at 75%, 50% and 25% of Etc (RDI-25%, RDI-50% and RDI-75%, respectively).
Maturity index increased with time, but olives from RDI-25 % are the most advanced. Oil and moisture content in olives didn't differ between irrigation treatments. Oil production increased with decreased water supply, RDI-25 % showed the highest production. Irrigation treatments may have an effect on oil composition. Total polyphenols and stability increased in olive oil from RDI-25 %. No differences in acidity and peroxide value were observed.

by R. T.
01 june 2009, Technical Area > Olive & Oil

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