Vine water stress and wine and grape quality

Vine water stress and wine and grape quality

Water stress and water emergence by 2040

Water stress is a temporary or prolonged condition of lack of water, usually lacking at ground level. As all plant stresses, it can result in primary damage or secondary damage to a plant.

According to the World Resources Institute's report (WRI), which measured the demand and availability of water in 167 states, the water emergency will be one of the most serious problems affecting our planet, not only in the poor but also In the most developed countries. By 2040, in fact, there will be 33 states that will face "extreme" water stress: about 14 of them are in the Middle East alone, with serious risks of political instability; but the scarcity of water resources, as the researchers say, will be evident also in other parts of the world including also some Italian and Balkan areas.

The drop in water resources - it is said in the report - was among the factors that forced 1.5 million people, mostly farmers and shepherds, to leave their lands for moving to urban areas, thus increasing the overall destabilisation of the countries. This phenomenon would also play an important role in the long conflict between Israel and the Palestinian Territories.

Researchers reveal that Chile, Estonia, Namibia and Botswana may also experience a sharp increase in water stress over the next 35 years, with repercussions on businesses, agriculture and the entire community. Even global superpowers such as the USA, China and India are not immune to the risks: water scarcity and water stress on crops, while remaining constant at national level, could increase between 40% and 70% in some areas, such as the Southwest Of the United States or the Chinese province of Ningxia, one of China's most promising wine producing regions that is already investing considerable resources for irrigation.

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Water stress in the vineyard

The vine is a plant that is well suited to arid hot environments. Many vineyard areas are characterized by limited seasonal precipitation, in some cases there is availability to irrigate and resort to planned irrigation or rescue operations, in other cases the inability to resort or, following the agronomic choice not to resort, involves a vegetative and reproductive development in limiting water conditions that we will define as a water deficit.

The water deficit limits the plant's vegetative and reproductive development. As for the ripening of the fruit, water deficiency conditions affect both the accumulation of primary metabolites and secondary metabolites and may have a positive influence on the quality of the wines. For this reason, in several vineyards, irrigation is forbidden as is the case with the French Appellation d'Origine Contrôlée (AOC) and as it was practised throughout Spain until many years ago.

Irrigation and management, however, remain an instrument in the hands of the farmer to optimize the productive performance of the vineyard. In particular, the application of a moderate and controlled water deficit makes it possible to produce the highest quality grapes, while maintaining a satisfactory plant productivity. On the other hand, an excessive water deficit leads to incomplete maturations with insufficient sugar degree and polyphenols with excessive astringency and bitterness.


Irrigation in the vineyard

Irrigation and its management, however, remain an instrument in the hands of the farmer to optimise the productive performance of the vineyard. In particular, the application of a moderate and controlled water deficit makes it possible to produce the highest quality grapes, while maintaining a satisfactory plant productivity. On the other hand, an excessive water deficit leads to incomplete maturations with insufficient sugar degree and polyphenols with excessive astringency and bitterness.

The scarcity of water resources for both agricultural and industrial and urban uses has in recent years shifted attention to modern and accurate water management in viticulture, in order to maximise its efficiency. The use of so-called irrigation strategies, which are based on irrigation plans that bring lower water levels to the evapotranspirational loss of crops during the season or during particular phenological phases, has become more and more common in fruit growing as well as in viticulture (Fereres e Soriano, 2007).

There are three strategies in viticulture: the so-called irrigation deficit (DI), regulated deficit irrigation (RDI), and partial rootzone drying (PRD) (Chaves et al., 2010).

The important practical and economic implications of these irrigation techniques have led researchers to carry out many studies on the topic, also in Friuli Region.

The results have often been contradictory and have shown dissimilar physiological responses between varieties and between different crop environments. In addition, many of these studies have only assessed the plant's production response to the water deficit, ignoring the aspect of the quality of the production, which in modern viticulture has taken on primary importance.

Over the past decade, the introduction of new molecular biology analysis techniques has led to a more detailed study of the physiological and metabolic response of the vine to the water deficit. In particular, much has been done to understand the effect of the deficit on the primary and secondary metabolism of the fruit, given the strong impact, this has on the quality of the wines.

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First experimental tests on water management in vineyard in Friuli: Pignolo and Sauvignon

Ersa, together with the University of Udine, already carried out tests in 2006 at the Tenuta Villanova Farm in Villanova di Farra d'Isonzo (GO) on the vineyards of Pignolo (Friulian autochthonous grape variety) and Sauvignon, both bred Guyot with distances of 0.70 mx 2.41 and 1 mx 2.40 to determine whether a reduction in water supply in the vineyard could maintain or improve the quality of grapes and wines.

To determine the water status of plants, an innovative parameter was used: the foliage potential, measured with the Scholander pressure chamber, which allows detecting on the single leaf the condition of hydration or water deficiency of the plant. This parameter, recently introduced from research into vineyard cultivation, has proved to be particularly useful in the optimum management of irrigation in vineyards.

The results of the tests have reported, in quantitative terms, that the production was not influenced by the imposed water stress. Differences between the theses were observed with regard to the quality of the grapes and wines obtained, highlighting an improvement in some analytical and sensory parameters of the theses subjected to water shortage.

Irrigation seems to have postponed the optimal phenolic maturation on the control thesis. The absence of water supplies accelerated the maturation of grapes under water stress. The sensory analysis of the wines of Pignolo also revealed organoleptic differences between the two theses. In stressful conditions, more intense smell, less acidic and more balanced taste, as well as a better wine structure.

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Effect of water stress on plant and grape content

At the same time as the experimental tests carried out with Ersa, the group of researchers at the University of Udine has started to deal with various water deficit projects, coordinated by prof. Enrico Peterlunger, focusing on the effect that the water deficit has not only on the physiology of the vine plant but also on fruit growth and metabolism.

Thus, a four-year experiment (2003, 2004, 2007, 2008)  on varieties such as Pignolo, Sauvignon, Merlot, Ribolla Gialla and Tokai, and a subsequent triennial experiment (2011,2012,2013) were conducted at the experimental agricultural company " A.Servadei "of the University of Udine.

From the research we can conclude, it can be concluded that imposing a moderate-severe water deficit in vineyards reduces production in quantitative terms but can positively influence the quality of the grapes to be transformed into wine; the imposition of an excessive deficit may slow down or prevent ripening of grapes with effects on quantity reduction but also on quality of production.

Although the deficit response is not unique among the different varieties, the deficit affects the content of primary and secondary metabolites of the fruit. Above all, the deficiency increases the synthesis of anthocyanin pigments and the concentration of proanthocyanidins (tannins) in red varieties.

Although the studies on this are still few, the synthesis of some volatile compounds and their precursors is also affected by the deficit. The effect of the deficit on secondary fruit metabolism has a positive effect on the organoleptic quality of wines. An accurate and fine modulation of the various techniques of oenological transformation of grapes under water deficiency can optimise the positive result in qualitative terms of controlled irrigation, leading to a finely finished product of higher value.

A detailed analysis of the physiological and molecular response of the various varieties to the water deficit will allow the grading of irrigation practices in vineyards in order to reduce the use of water resources and optimise the quality of wines also in relation to the other environmental factors characterising the different national and international viticulture areas.

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Automated irrigation management in the vineyard: the Italian-Israeli "Irrigate" project

Developing an automated irrigation management program through climate, plant and soil controlling sensors to manage the impact of drought on vine productivity and grape quality is the goal of the Italian-Israeli bi-annual research project "Irrigate", launched in 2014 and co-ordinated by the University of Udine and supported by the Italian Ministries of Foreign Affairs and the Israeli Industry, Trade and Work.

"The project," explains coordinator  Enrico Peterlunger of the University of Udine, "created with Israeli partners, a world leader in irrigation and drought technologies, stems from the fact that in recent years the vine cultivation has been subject to new threats linked to increasingly unfavourable weather conditions.In recent years, droughts have been intensified, including the areas characterized by non-limiting water availability for its cultivation, such as Friuli Venezia Giulia, where in recent years the Summer drought has led to a significant drop in production, sometimes negatively affecting the quality of wines. This study will benefit both Friuli and Israeli viticulture, and will also have a positive impact on other Mediterranean viticulture areas. "

The project first involves the study of the physiological mechanisms that regulate the response of the vine in water shortages to limit the negative effects on the quality and quantity of the production. At the same time, an "intelligent" and automatic irrigation control program will be implemented in the vineyards to allow optimal water quantities to maintain yields and optimise production quality during drought periods.

Partner del progetto sono il dipartimento di Scienze agrarie e ambientali dell’Ateneo friulano e il centro di ricerca IGA, e, per parte israeliana, l’istituto di Biotecnologia e Agricoltura delle zone aride dell’Università Ben Gurion nel Negev e la società Netafim.  

"Irrigate - Automated irrigation management through integrated climate-plant-soil sensing to prevent water shortage's impact on yield and quality grape" is part of the Cooperation Agreement in the field of industrial, scientific and technological research and development between Italy and Israel. Project partners are the Agricultural and Environmental Sciences Department of the Friuli-Venezia Giulia University of Udine, IGA, Research Center, and the Israeli Department of Biotechnology and Agriculture of the Arid Areas of Ben-Gurion University of the Negev and Netafim Society.

Patricija Muzlovic, Paolo Sivilotti

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Related questions

  • We talk a lot about sustainability in agriculture and in viticulture in particular. What is it about?

    Sostenibilità e sviluppo si incontrano e si integrano a vicenda nel concetto di “Sviluppo Sostenibile”, che negli ultimi 20 anni è stato oggetto di diverse interpretazioni. La definizione più famosa è quella del Rapporto Bruntland (1987) che vede nella sostenibilità lo "sviluppo che risponde alle necessità del presente, senza compromettere la capacità delle generazioni future di soddisfare le proprie necessità". Un’altra definizione “storica” è quella formulata nel 1991 in “Caring for the Earth: A Strategy for Sustainable Living” dove la pratica dello sviluppo sostenibile è “il soddisfacimento della qualità della vita, mantenendosi entro i limiti della capacità di carico degli ecosistemi che ci sostengono”. Le due definizioni danno assieme una chiara comprensione del concetto di Sviluppo Sostenibile inteso come beneficio per le persone e per gli ecosistemi. Il Summit mondiale di Rio De Janeiro (1992) ha segnato un passaggio storico nella consapevolezza del problema ambientale planetario, che non può essere affrontato riparando i danni a posteriori, ma riorientando il modo di produrre e consumare verso la qualità ambientale e sociale. Il World Summit on Sustainable Development (WSSD) di Johannesburg (2002) ha ampliato il concetto di Sviluppo Sostenibile come integrazione di tre dimensioni, strettamente collegate tra loro:

    • Economia (povertà, modelli di produzione e consumo...)
    • Società (pace, sicurezza, diritti e libertà fondamentali, diversità culturali...)
    • Ambiente (protezione e gestione delle risorse naturali...)

    Lo Sviluppo Sostenibile può quindi essere considerato come un equilibrio dinamico tra qualità ambientale, istituzionale, sviluppo economico e equità sociale: non mira al mantenimento di uno “status quo”, ma si muove invece nella direzione del cambiamento, riconoscendo che la società umana è in costante movimento.

    Solo dal 25 settembre 2015, con la nuova “Agenda 2030” dell’ONU, tutti i paesi del mondo senza distinzioni tra ricchi e poveri, avanzati in via di sviluppo, hanno sottoscritto l’impegno a perseguire nei prossimi 15 anni  I 17 obiettivi comuni per lo sviluppo e la salvezza del pianeta, che non sono soltanto di natura ambientale ma anche sociale ed economico. Gli Obiettivi di Sviluppo Sostenibile hanno così sostituito da quest’anno gli Obiettivi di Sviluppo del Millennio (scaduti nel 2015), chiamando tutti i paesi del mondo a formulare una strategia di sviluppo universale adeguata senza distinzioni tra paesi sviluppati, emergenti e in via di sviluppo. Infine, l’agenda è frutto di un grande processo partecipativo al quale possono tutt’ora contribuire tutti, dalla società civile, mondo politico, mondo scientifico e produttivo.

    Su iniziativa dell’Università Tor Vergata di Roma e della Fondazione Unipolis, è nata invece a febbraio 2016, Alleanza Italiana per lo Sviluppo Sostenibile (ASVIS) che mette insieme un gruppo di lavoro trasversale a più settori e a più mondi creando una rete virtuosa composta al momento da un centinaio di membri. La sua missione è di raccogliere e declinare su scala nazionale la sfida divenuta oggi più che mai globale della sostenibilità. L’alleanza è stata ufficialmente presentata alla Camera dei deputati davanti alla presidente Laura Boldrini e al ministro dell’Ambiente Gian Luca Galletti l’11 marzo 2016. 

    Il concetto di “agricoltura sostenibile” è molto ampio e complesso. Può essere visto dal punto di vista ambientale, intendendo un'agricoltura rispettosa delle risorse naturali quali acqua, fertilità del suolo, biodiversità, e che non utilizzi sostanze chimiche inquinanti. Si può parlare di agricoltura sostenibile dal punto di vista sociale, cioè la capacità dell'intera produzione agroalimentare mondiale di far fronte alla domanda globale, non solo dei paesi industrializzati, ma anche di quelli in via di sviluppo. Si può, infine, intendere l'agricoltura sostenibile, dal punto di vista economico, cioè vantaggiosa per l'agricoltore favorendo un reddito equo (commercio equo-solidale), la tutela della salute dell'operatore e il miglioramento della qualità della vita degli agricoltori e dell'intera società. Chi si occupa di agricoltura sostenibile, privilegia pertanto quei processi naturali che consentono di preservare la “risorsa ambiente”, evitando così il ricorso a pratiche dannose per il suolo (come le lavorazioni intensive) e a sostanze chimiche (pesticidi, ormoni, ecc.) e utilizzando fonti energetiche rinnovabili. Non esiste un unico modo per fare agricoltura sostenibile (dalla agricoltura biologica, biodinamica, permacultura, agricoltura sociale, agricoltura solidale ed infine, agricoltura integrata). 

    La sostenibilità è un argomento centrale nel mondo viticolo ed enologico, ma dare una definizione univoca di tale concetto può a volte essere difficile, dal momento che i sistemi agricoli sono complessi e caratterizzati da differenti gradi di dinamismo, e coinvolgono spesso visioni e approcci fondamentalmente differenti in funzione di obiettivi e valori in campo. In ogni caso, l’agricoltura, nel caso specifico, le viticolture attuali portano con loro una serie di problemi legati ad insicurezze economiche date dal momento storico in cui ci troviamo, necessità ecologiche, di ovvia natura, e fabbisogni sociali che richiedono interventi mirati e tempestivi. Partendo da ciò, la definizione di viticoltura sostenibile non può prescindere da un’accezione pratica che trovi riscontri applicativi nelle realtà produttive. Constatando l'esistenza di diversi approcci e regolamenti nazionali relativi in particolare alla produzione ragionata, integrata e sostenibile, l'OIV (Organizzazione Internazionale del Vigneto e del Vino) ha deciso di armonizzare tali approcci e di apportarvi le specificità proprie al settore vitivinicolo già nel 2004. Pertanto, l’OIV ha adottato la definizione e i principi generali dello sviluppo sostenibile applicato alla vitivinicoltura (CST 1-2004) in quanto segue: "Approccio globale commisurato ai sistemi di produzione e di trasformazione delle uve, associando contemporaneamente la longevità economica delle strutture e dei territori, l’ottenimento di prodotti di qualità, la presa in considerazione delle esigenze di una viticoltura di precisione, dei rischi legati all’ambiente, alla sicurezza dei prodotti, alla salute e dei consumatori e la valorizzazione degli aspetti patrimoniali, storici, culturali, ecologici ed estetici." Per rispondere a questa definizione, nel 2008 l'OIV adotta una guida per l'attuazione del concetto di sviluppo eco-sostenibile nel settore vitivinicolo mondiale (CST 1-2008).

     Secondo la Risoluzione CST 1/2008 dell’OIV i punti fondamentali per una viticoltura sostenibile toccano i seguenti ambiti:

    • produzione delle uve,
    • trasformazione delle uve in vino;
    • condizionamento dei prodotti (confezionamento e stoccaggio).

    Patricija Muzlovic