Estratégias de rega deficitária em vinha – indicadores de carência hídrica e qualidade

For most of the Portuguese viticultural regions, soil water availability is one of the main limitations in vineyards management, with negative consequences for the wine quality and farmers’ income. Thus the improvement of wine quality by irrigation is the key factor for the reinforcement of the competitiveness of this sector. With this purpose, it is crucial to establish relationships between irrigation strategies (deficit irrigation regimes and irrigation scheduling) and grape quality. Therefore, the present research will be conducted to enhance understanding of the responses of grapevines to water use in three regions (Douro, South Alentejo and Setubal Peninsula), which were selected for its representative ness and extreme climatic conditions. The main objectives are to (i) quantify evapotranspiration (ET) and crop water requirements along the vegetative cycle using eddy covariance and sap flow techniques (tasks 3 and 4); (ii) evaluate water stress indicators for irrigation scheduling, identifying threshold values mainly for those that can be automated (e.g. relative transpiration, variations in trunk diameter) and studying their relations with well established and not automated ones (e.g. predawn leaf water potential, stomatal conductance, soil water balance) (task 5); (iii) assess the responses of crop growth, yield and must quality to different water application strategies and cover crops (tasks 6 and 7). In order to achieve the defined objectives, direct crop coefficients (Kc) will be determined in standard well-irrigated plots. Stress coefficients (Ks) obtained from different deficit irrigation regimes will be related with grape quality variables (e. g. aroma compounds, flavour precursors and phenolic compounds). On the other hand, relative transpiration will allow the development of a robust scheme for irrigation scheduling. The relationships with the other water stress indicators will enhance the knowledge for regions where the coefficients (Kc and Ks) are not locally available. Cover crops will be used with the objectives of reducing soil erosion and increasing soil moisture depletion in spring in order to impose earlier regulated vine water deficits, which may improve grape quality. Additionally, methodological analysis of sap flow thermal heat dissipation techniques together with soil evaporation measurements will enable long term estimations of ET components. At the end of this project, the interdisciplinary research team, that comprises several Ph.D. degrees in this field, intends to validate a methodology for the definition of water stress thresholds adjusted to the optimisation of wine quality. This would contribute to drawing guidelines for improved water management programmes in viticulture.