The majority of the cultural cares of the olive tree, like for example the irrigation, the fertilization and the pruning, has a great influence concerning production but they influence little in the quality of the obtained oil. Nevertheless determined phytosanitary treatments are decisive to secure quality.
In those areas where rain is a limiting factor for the production and, unfortunately, it is it in the province of Jaén and in most of the Spanish olive growing areas, the irrigation is an advisable cultural technique from the point of view of the production, since the production can increase between 50% and the 100% given by an increase of the size of the fruits and the number of fruits materialized by the plant.
The amount of water necessary to water the olive grove is much smaller than for other breedings. For example, fruit trees need 7.000 m3/ha whereas traditional olive grove needs only 2.000 and the intensive olive grove about 3.000. But considering the lack of water that suffers this area, one of the main targets is to optimize the use of it. The present state of technical knowledge on the irrigation of the olive grove allows to program the irrigations to obtain the maximum production.
On the other hand, like any other breeding, the olive grove receives water of rain. The rainwater, in normal climatic conditions, can contribute between a 60% and a 75% of the necessary the total water. The objective is to take advantage, as it is possible, of the rainwater and, to this end, it is important to reduce the amount of water evaporated from the ground. Everybody is almost conscious of the losses of water due to the impermeability of grounds, but almost nobody knows that by evaporation from the superficial layers a great amount of water is lost, losses that in this climate can be evaluated up to a 50%. All savings in the evaporated amount of water takes to a benefit to the olive grove, and in the case of an irrigated olive grove, to a reduction of the contributed water, that in the area of this province is expensive although it is underground water or river water, the pumpings are very deep, and so the power costs are elevated.
As far as the ground workings concerns, the working or the plow has always been seen as very favorable for the breeding, since on the one hand it eliminates the vegetal layer that absorbs water and on the other it increases the capacity of infiltration of the ground. Nevertheless, it is necessary to consider that the infiltration in the top layer of the ground is increased and that can be seen reduced in deeper layers due presence of grounds that retain water in the surface favoring the evaporation. In addition the effect to the working is perishable, since the infiltration increases after the work is realized, but after an intense rain it is reduced drastically and only repeated workings could do that water could infiltrate. But, nevertheless, it has been verified that a single work in a year can be sufficient to maintain higher rates of infiltration in the ground.
This is because the working favors the appearance of the work soles, which are those hardened ground layers due to the passage of the workers. The maintenance of a vegetal cover of grass during the winter is the most effective form to increase the infiltration and to avoid the appearance of those hardened superficial ground layers. Far from being able to say that all work is an irrigation, we can say that it is an important water wastefulness, mainly when the workings are realized in spring with equipment that rip the ground. The reduction of the workings in spring favors the conservation of the water since the scab that forms in no wrought grounds is a trap that reduces the losses by evaporation.
Another important cause of loss of water is the presence of bad grass in spring, mainly if we think that those bad grasses, besides consuming water, demand workings to control them that force to lose still water more. For that reason the use of weed killers is advised in spring before the use of disc launching slips for its eradication.
As far as the quality of obtained oils, this one is independent of the use or not of fertilizers. As far as the pruning, it must contribute to maintain the crown ventilated and perfectly illuminated, for which the form of the plant must be that one that allows a greater illuminated surface and with the pruning of smaller branches that makes a good production compatible with a good size of the fruits. In addition it would have to adapt the tree to the mechanization of the harvesting; to avoid the damages caused to the fruits in the harvesting by “vareo” (hit the tree with a stick to make the olives fall).
Finally, the vegetal or phytosanitary protection of the olive tree by fumigation is without a doubt the culture technique that more influence has in the quality of the obtained oil. The plagues and diseases that attack the olive tree can classify according to the damages that they cause to the fruit in:
– Those that favor the fall of the mature or almost mature fruits, like “barrenillo”, “repilo”, “escudete” or the fly.