Olive Tree Physiology & Chemical Composition Of Fruits Are Modulated By Different Deficit Irrigation Strategies

28/10/19:   High irradiation levels, warming of the climate, drought, and lower water availability have been a reality over recent years and the future predictions indicate that this trend may continue.  The challenges in modern olive production may need to consider strategies for olive grove management and take into account the latest peer-reviewed research from Portugal which delves into deficit irrigation strategies.

The study assessed Irrigation Strategies including:

  • full irrigation (FI, 100% ETc)
  • three deficit irrigation strategies (DIS):  regulated deficit irrigation (RDI), irrigated with 80% of crop evapotranspiration (ETc) in phases I and III of fruit growth and 10% of ETc in the pit hardening stage)
  • two continuous sustained strategies (SDI), a conventional SDI (27.5% of ETc)
  • low-frequency irrigation adopted by the farmer (SDIAF, 21.2% of ETc)

Different Deficit Irrigation Strategies (DIS) has shown beneficial effects on fruit yield, being sustained deficit irrigation (SDI) and regulated deficit irrigation (RDI) two of the most common strategies.  In SDI, a constant application of a reduced amount of water, which can be defined as over 75% to less than 25% of the crop evapotranspiration (ETc), leads to a slow gradual increase of water deficit as the season advances, allowing plants to adapt
to it.

An example in the study has shown that for a Californian high-density hedgerow  ‘Arbequina’ olive orchard, fruit yield could be maximised with an SDI strategy using 70 to 75% of ETc, being the best results in olive oil chemical parameters, flavour & stability achieved with 33 to 40% of ETc.

Researchers noted “In olive trees, the main objective of RDI is not to control vegetative growth, since shoot growth occurs mainly in spring and
slightly in autumn.  Additionally, it has been noticed that deficit irrigation significantly reduces the final yield if applied in spring, from bud-burst until fruit drop, and in late summer during fruit oil synthesis.  Conversely, if applied during summer, specifically during the fruit pit-hardening phase, deficit irrigation could result in a lower reduction in fruit and oil yield.”

“It was found that the newly applied irrigation systems (FI, RDI & SDI) improved plant performance in relation to the system adopted by the farmer (SDIAF), including water status and net photosynthetic rate.   By the end of the summer season, the leaves from all DIS treatments developed higher tissue density and, in general, presented changes in secondary metabolism, with higher accumulation of phenolic compounds, responses that boost drought resistance.  Although the newly applied irrigation systems improved crop yield in parallel with the volume of water applied, the water productivity tends to decrease.” said Researchers.

Evaluating the best use of water which is the primary resource for commercial olive production, can certainly bring benefits of crop load management, water productivity and accumulation of phenolics.  The results of this study concluded that deficit irrigation strategies are essential for sustainable olive growing in regions of limited water resources.

_____________________________________________

Drought Stress Effects and Olive Tree Acclimation under a Changing Climate

Aim

Hence, in this work, we aimed to understand the response of 8 years old “cv. Cobrançosa” olive trees to three deficit irrigation strategies, RDI and 2 SDI treatments, in order to optimize the use of water in crop production. To accomplish this objective, we studied the irrigation regimes’ effect on the plant water status, photosynthetic performance, foliar primary and secondary metabolites fluctuations, and fruit yield as well as quality parameters.

Abstract

To overcome constraints affecting olive groves, cropping practices focusing on agronomic water use efficiency and their impact on quality parameters must be investigated. We evaluated the response of olive trees (Olea europaea, cv. Cobrançosa) to different water regimes, full irrigation (FI, 100% ETc) and three deficit irrigation strategies (DIS) (regulated (RDI, irrigated with 80% of crop evapotranspiration (ETc) in phases I and III of fruit growth and 10% of ETc in the pit hardening stage) and two continuous sustained strategies (SDI), a conventional SDI (27.5% of ETc), and a low-frequency irrigation adopted by the farmer (SDIAF, 21.2% of ETc).

Results
The effects of water regimes on the plant water status, photosynthetic performance, metabolites fluctuations and fruit quality parameters were evaluated. All DIS treatments enhanced leaf tissue density, RDI and SDI generally did not affect leaf water status and maintained photosynthetic machinery working properly, while SDIAF treatment impaired olive tree physiological indicators. DIS treatments maintained the levels of primary metabolites in leaves, but SDIAF plants showed signs of oxidative stress.

Moreover, DIS treatments led to changes in the secondary metabolism, both in leaves and in fruits, with increased total phenolic compounds, ortho-diphenols, and flavonoids concentrations, and higher total antioxidant capacity, as well higher oil content.

Phenolic profiles showed the relevance of an early harvest in order to obtain higher oleuropein levels with associated higher health benefits.

Conclusion
Adequate DIS are essential for sustainable olive growing, as they enhance the competitiveness of the sector in terms of olive production and associated quality parameters.

Authors: Alexandre Gonçalves, Ermelinda Silva,  Cátia Brito, , Sandra Martins,  Luís Pinto,  Lia-Tânia Dinis, Ana Luzio, Carlos Martins-Gomes, Anabela Fernandes-Silva, Carlos Ribeiro, M. Ângelo Rodrigues, José Moutinho-Pereira, Fernando M. Nunes, Carlos M. Correia

  • CITAB—Centre for the Research and Technology of Agro-Environmental and Biological Sciences, University of Trás-os-Montes and Alto Douro, 5000-801 Vila Real, Portugal
  • Research Mountains – Association, Brigantia Ecopark, 5300-358 Bragança,
    Portugal
  • CQVR – Chemistry Centre of Vila Real, Universidade de Trás-os-Montes e Alto
    Douro, 5000-801 Vila Real, Portugal;
  • Agronomy Department, University of Trás-os-Montes and Alto Douro, Quinta dos
    Prados, 5000-801 Vila Real
  • Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança,
    Campus de Santa Apolónia, 5300-253 Bragança, Portugal

Read the full study at Journal of Science of Food & Agriculture

 

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