Acquavitis

PORTAL ACQUAVITIS
The Acquavitis interactive portal (www.acquavitis.eu) enables the systematic collection of agrometeorological parameters, geo-visualization of satellite, environmental and other spatial data to help us interpret data on water stress in vineyards and water status in soils and plants. With quick and transparent information, we can prepare for increasingly frequent extreme situations such as water stress in viticulture.

HYDROLOGICAL CYCLE
When faced with drought, water supply and rational water use, it is also crucial to know about water cycling. Over the two years of the project, the isotope method applied to rainwater, soil and xylem sap has allowed us to understand how vines replenish and use groundwater. The importance of winter and spring rainfall in replenishing soil water, even in the deepest layers, was highlighted. Summer rainfall is usually absorbed only in the most superficial layers of the soil and is immediately used by the vines. Winter-spring recharge, therefore, represents an additional strategic resource, particularly during severe drought periods. Understanding these processes was also made possible by the additional sampling campaign carried out for the Ceroglie site in 2021, which allowed us to correlate individual rainfall events with a larger number of soil samples and xylem sap. Data with higher temporal resolution allow a better understanding of the eco-hydrological processes, but it must be borne in mind that each vineyard has its own characteristics, which depend on both the geomorphology/geology of the site and the specificities of the plant (e.g. age of the vineyard, vineyard used, cultivar and substrate). With this in mind, the method developed in the framework of the present project has proven to be effective and therefore represents a valid tool for site-specific analysis.

MONITORING THE WATER STATUS OF VINES
Monitoring the water status of vines using a pressure chamber is an important tool for quantifying water stress levels and for optimising and efficiently managing irrigation during the growing season. Therefore, the pre-dawn water potential (an indicator of the availability of soil water to the plants), the minimum daily leaf water potential (an indicator of the maximum water stress suffered by the vine) and the minimum daily stem water potential were measured in the six main vineyards of the Acquavitis project during the 2020-2021 biennium. In addition, we monitored vine stem water potential in 14 vineyards of the Merlot variety in the Vipava Valley, comparing vineyards on terraces and hills (n=7) and in lowland vineyards (n=7). No particular criticality in terms of soil water availability for plants was highlighted during the two years of the study, but during the hottest months (end of July and end of August) in 2021, a marked increase in water stress was observed relative to Ψsteblo measurements in three of the six study sites, which achieved moderate to high water stress. Vines in the terraced vineyards of the Vipava Valley also showed water stress in July and August. The results showed that vine water stress resulted in a lower yield per vine (25 to 60%) in the terraced vineyards compared to the lowland vineyards. On the other hand, Merlot wines on the terraces contained on average more total dry extract and ash, more anthocyanins (colouring agents) and 20-35% more tannins compared to wines made from grapes from lowland vineyards in the Vipava Valley. The project also carried out some methodological tests to correctly measure water potential. From these tests, it was found that the leaf retention time between harvesting and the measurement of leaf water potential depends on the variety studied and/or the level of water stress achieved. This underlines the importance of developing specific protocols in individual vineyards before field monitoring is carried out.

REMOTE CONTROL FOR MONITORING WATER STRESS IN VINEYARDS
The main focus of the use of remote sensing in the Acquavitis project was the use of different sensors on different platforms to monitor the water status of selected vineyards. In the Komno vineyard, we used a multispectral camera and hyperspectral cameras on a drone, which together capture a signal with wavelengths of 400 - 2500 nm. Correlations between plant water potential measurements and remote sensing data from all three sensors were confirmed. Regression models have been developed to determine vine water stress, but the accuracy of the models varies between sensors and with the level of water stress expressed. In general, the most accurate models were obtained from hyperspectral data taken with an ultralight aircraft, but more field data would need to be included in the models of all tested sensors to produce a reliable method for monitoring water status in vineyards. Vineyards in the area of Precenicco, Strnc and Budihni were monitored using multispectral imagery from the Sentinel-2 constellation. Sentinel-2 is a constellation of two satellites of the European Space Agency's Copernicus programme. Sentinel-2A and Sentinel-2B capture multispectral data with an optical sensor covering 13 channels. The images are captured in visible light, near-infrared and short-wave infrared spectral ranges. Water potential
The leaf water potential measured before dawn, the minimum water potential as well as the stem water potential provide a reliable estimate of the water status of the vines in relation to the water available to the plants and the meteorological conditions. We found that the leaf water potential before dawn is strongly correlated with some wavelengths. The correlation is pronounced in the infrared spectra. In the future, we can expect a wider use of remote sensing data to determine the water status of plants. As confirmed in our project, multispectral, and especially hyperspectral, data are very useful for this purpose. The synergy of aerial, drone and satellite imagery can be a very effective instrument for monitoring the condition of plants over different areas while allowing appropriate action to be taken in the production and processing of grapes.

RATIONAL IRRIGATION AND SOIL MANAGEMENT
Evaluating irrigation guidelines is a challenge for winegrowers because many variables are involved and seasons vary widely. In the context of the project, the use of the DSS Vintel® allowed different irrigation strategies to be tracked and it was possible to verify how moderate water stress from flowering to harvest allowed the vines to be kept in good physiological condition. Yields were slightly reduced, but this did not compromise the quality of the grapes. On the other hand, several threshold levels of water stress caused damage to the plants, which in turn affected the quality of the grapes and wines. The rational use of water in viticulture also involves appropriate and sustainable soil tillage. Thus, the project has focused on research into green manuring technologies, where different mixtures of grasses and/or leguminous crops are used to retain soil moisture. The measure can be useful both in the case of excess rainfall in spring, where the crops are allowed to grow higher, thus improving evapotranspiration and soil drying, or in the other extreme in drought, where bending (roller-blading) allows better coverage and soil moisture for longer periods of time.