Water status is one of the most critical factors in vineyard management, especially in regions where water scarcity and rising temperatures are reshaping viticulture practices.
Ensuring vines receive sufficient—yet not excessive—water is essential for maintaining both yield and quality. In this context, a team of experts including Markus Rienth, Cécile Laurent, and Thibaut Scholasch recently published a review (authorized for reprinting by the International Viticulture and Enology Society, IVES) that evaluates the latest scientific advances in plant-based methods for assessing vine water status.
Unlike soil or environmental measurements, which offer indirect insights, plant-based approaches provide direct information on how the vine itself responds to water availability. These methods help vineyard managers fine-tune irrigation strategies, optimize grape quality, and mitigate stress under increasingly challenging climatic conditions.
Visual Observation
Visual assessment remains the most accessible method. Growers can detect early signs of water stress, such as tendril wilting, leaf rolling, or slowed vegetative growth. However, this technique is limited: symptoms often appear only after stress has already set in, and they can easily be mistaken for effects caused by other issues, such as nitrogen deficiency or atmospheric stress. Recently, mobile applications have been developed to assist growers in identifying symptoms more reliably.
Water Potential Measurement
One of the most widely used direct methods is measuring water potential with a pressure chamber. By assessing the pressure required to force water out of the leaf or stem, growers gain insights into the tension driving water movement within the plant. Measurements taken before dawn or at midday provide valuable information, though they are influenced by external conditions such as cloud cover or evaporative demand. Another complication arises when cavitation occurs—air bubbles forming in the xylem—which can lead to overestimation of stress levels.
Carbon Isotopic Discrimination
Carbon isotope analysis (13C/12C ratio) offers a retrospective view of vine water status across a season. When water or nitrogen is limited, discrimination against 13C decreases, leading to higher isotope ratios in sugars, musts, or wines. This makes isotopic analysis a powerful tool for evaluating vineyard management strategies over time, but it does not provide real-time data and therefore cannot guide daily irrigation decisions.
Sap Flow Measurement
Sap flow methods track the actual movement of water through the vine. Two primary approaches exist:
- Thermal probe method: Involves inserting heated and reference needles into the stem to measure temperature differences. Accuracy can be compromised by improper placement or internal stem variability.
- Stem thermal balance method: Uses a heating sleeve around the stem, offering a non-invasive alternative that reduces interference from non-conductive tissues.
Sap flow monitoring provides continuous data, making it well-suited for detecting short-term stress episodes. However, it requires specialized equipment and installation, limiting its widespread adoption.
Balancing Representativeness and Precision
A major challenge with plant-based methods is that they are typically applied to a small number of vines within a vineyard. Since water status can vary significantly across plots, careful selection of sampling points is essential to ensure results represent broader vineyard conditions.
The Need for Integrated Data
Each technique has advantages and limitations:
- Visual symptoms emerge only after stress occurs.
- Water potential can be skewed by cavitation or environmental fluctuations.
- Isotopic analysis integrates seasonal effects but misses short-term variations.
- Sap flow provides continuous data but requires technical expertise.
Ultimately, plant-based methods should not be used in isolation. They are most effective when combined with soil moisture monitoring and atmospheric data (such as vapor pressure deficit). Only by integrating plant, soil, and climate information can growers optimize irrigation, applying the minimum necessary water while safeguarding both vine health and fruit quality.
Looking Ahead
As climate change intensifies water scarcity, improving water-use efficiency in vineyards is becoming a central priority for viticulture worldwide. Plant-based monitoring methods provide invaluable insights into vine physiology and responses to water stress. When coupled with digital tools, continuous sensors, and precision viticulture approaches, these methods are helping pave the way toward more resilient, sustainable vineyard management.
Source: Vinetur