Researchers from Universidad Politécnica de Madrid (UPM), Center for Soil Science and Applied Biology Segura (CEBAS-CSIC), Institut des Biomolécules Max Mousseron (IBMM) from Université de Montpellier and the Centro Agrario El Chaparrillo of Castilla-La Manchahave carried out an experimental work for irrigation of an olive grove in order to verify the effects on water stress on both the quantity and quality of the resulting oil. After two years of research, they proved that the usage of regulated deficit irrigation does not affect on the quantity of production, but it does causes a content increase of phytoprostanes in the oil which are beneficial components to health, therefore it seems to be a good practice for irrigation of olive groves since, besides, It is more sustainable for the environment.
Olive oil is one of the main components of the Mediterranean diet and Spain, with 2.5 million hectares of cropped area, its main producer. Recent studies suggest links between various olive oil components and their beneficial effects on health. In this sense, it is important to highlight that this functional food has high levels of monounsaturated acids such as oleic acid which has beneficial effects on cardiovascular and liver health. Besides, olive oil has multiples minor components such as polyphenols that have a high biological activity.
Phytoprostanes are other minor components present in olive oil which are not only excellent biomarkers of oxidative degradation products of plants, but also are considered biologically active molecules as they are components of an archaic signaling system to protect plants against oxidative damage. These components are found in free and esterified plants. However, due to lack of enough enzymes for hydrolyzing esters, only those found in their free form are absorbed by our body. Although little is still known about its biological effects, there are evidences that phytoprostanes can help to modulate the function of the vascular system and immune system.
Despite the fact that olive crops are traditionally developed in dry conditions, it has been proved that irrigation is an essential practice to improve olive oil production and productivity. However, over the last years, there have been other problems apart from arid climate conditions and persistent water shortages such as the strong competition with other non-agricultural users. Thus, in order to face this water scarcity, a sustainable irrigation has to combine a production increase with minimal water usage.
Thus, a group of researchers from UPM, CEBAS-CSIC, IBMM and from the Centro Agrario El Chaparrillo experimented with a particular practice of irrigation: regulated deficit irrigation (RDI) that consists of restricting irrigation during the phases in which water stress have no impact on production.
This research was carried out in an olive grove of the Cornicabra variety with an area of 7x5 m in Ciudad Real. During two years, 2012 and 2013, researchers conducted a control treatment, watered to avoid water stress and three RDI treatments. As a result of the last treatments, diverse levels of water stress were triggered during the phase of pit hardening.
It was observed that although water stress does not affect on quantity production it does affect on its quality thanks to an increase of phytoprostanes which are beneficial for health. Researchers have found that the level of phytoprostanes changes every year, possibly due to environmental conditions or due to tree loads. This may be a topic for future research.
Regulated deficit irrigation (RDI) is therefore a recommended practice for irrigation of olive groves to achieve healthier food apart from being more sustainable.
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