Influencia del régimen hídrico en el comportamiento fisiológico, agronómico y de calidad de la producción en cultivos mediterráneos

Resumo

The almond tree [Prunus dulcis (Mill.) D.A. Webb] and the grapevine (Vitis vinifera L.) are two of the most important perennial crops in the Mediterranean basin, especially in the two countries that make up the Iberian Peninsula, Spain and Portugal. These two crops represent great economic value in the rural regions where they are established, and the transformation industries (e.g. almonds products and wine) generate important economic activity associated with numerous direct and indirect jobs. The almond tree and the grapevine perfectly adapt to the edaphoclimatic conditions of the Mediterranean region. However, in the last years, climatic changes have been a new handicap for the profitability of both crops. Moreover, the predictions of climate change for the near future, a decrease in precipitation and an increase in temperatures will not be favorable for these crops. In this order, strategies are currently being found and implemented to mitigate the negative effects of water stress, high temperatures and high radiation in Mediterranean summers. Irrigation is one of the best strategies to mitigate the problems associated with adverse climatic summer conditions. However, water scarcity and the high cost of irrigation infrastructure are limiting factors for its use. For this reason, other mitigation strategies, such as foliar application of reflector substances such as kaolin, are being investigated. The main objectives of this thesis were to study the effects of different deficit irrigation strategies and kaolin foliar application on the physiological activity and yield in almond trees cultivated in the northeast of Portugal and, at the same time, evaluate the influence of these deficit irrigation techniques in different almond quality parameters. Thus, these strategies were applied to three almond cultivars, namely Ferragnès, Vario and Constantí, to evaluate the differences in behavior between them. Regarding the vineyard, there are already many studies that have evaluated the effects of deficit irrigation on the physiology of the grapevine and the quality of the grapes and wines. Thus, the present work was focused on the use of the sector's byproducts wine industry to promote sustainability and, at the same time, to increase their added value. As deficit irrigation has been a widespread technique in recent years in viticulture in the Iberian Peninsula, it is important to know the effects of different water regimes on the physicochemical and biochemical composition, as well as the antioxidant capacity of the by-products. Therefore, the effects of different water regimes on two by-products, vine leaves and grape seeds, were evaluated. To this purpose, two experimental field studies were carried out in two different vineyards in the Douro Demarcated Region (Portugal). Almond trees under regulated deficit irrigation during the grain filling phase presented a higher level of water stress but with few effects on their physiological activity. Regarding the accumulated productivity during three years of experiment, the two cultivars evaluated showed different responses. On the one hand, the cultivar (cv.) Constantí did not present a significant reduction in its productivity when regulated deficit irrigation was applied compared to the full irrigation treatment; on the contrary, the cv. Vairo showed a significant reduction. As expected, sustained deficit irrigation improved the productivity of cv. Ferragnès compared to rainfed almond trees and did not present significant productivity reductions when the reduction in deficit irrigation was moderate (70% ETc). The foliar application of kaolin did not show effects on productivity or physiological activity in the two field experiments in which it was evaluated. In general, the quality parameters of the almonds (morphological characteristics, color, nutritional composition, fatty acid composition, tocopherols, tocotrienols and volatile composition) did not show a reduction when different deficit or kaoline irrigation strategies were applied. Grapevine leaves had a high concentration of phenolic compounds, which was correlated with high antioxidant capacity. In this sense, the increase in the amount of water provided by deficit irrigation caused a decrease in the concentration of this type of compounds. The leaves collected during the phenological stage of veraison were those with a significantly higher richness in phenolic compounds. Deficient irrigation caused a reduction in the weight percentage of seeds within the total weight of the grapes. Grape seeds had a high oil content with high polyunsaturated fatty acids, tocopherols and tocotrienols, highlighting that deficit irrigation increased the concentration of total tocopherols and decreased that of tocotrienols. In conclusion, the different deficit irrigation strategies implemented in the almond tree experiments obtained favorable results in terms of physiological response and yield when compared to the rainfed almond trees. Furthermore, these strategies also contributed to saving water without affecting the yield when compared to almond trees under full irrigation. The quality of the almonds was not reduced by the application of deficit irrigation or kaolin; it even improved some of these parameters, such as tocopherols and volatile compounds concentration. Grapevine leaves and seeds can be two by-products of the wine industry with added value in which the water regime greatly influences their physical, chemical and biochemical composition.