Exploring the interaction between radiation availability and grapevine canopy physiology across different agrivoltaics configurations

The intricate interplay among agrivoltaics (AV) covers, light interception and distribution, and grapevine canopy physiology remains largely unexplored. In mature Cabernet Sauvignon vines, we assessed the physiological effects of different AV module settings compared to open field (OF) conditions: dynamic tracking (DT), which maintains an anti-tracking mode in the morning and switches to sun-tracking from 1:30 PM onward; sun anti-tracking (SAT); and fixed horizontal (FH). Vine microclimate and whole canopy gas exchange were continuously monitored across these settings for 7, 25, and 101 days, respectively. Under FH orientation, light extinction measured with a single hemispheric sensor placed horizontally above the canopy was a reliable predictor of whole canopy light availability as it led to a slight under-estimation (-1.7%) as compared to a vertical light canopy scanning. In contrast, a larger underestimation (-10–15%) occurred for DT and SAT. There was no direct proportionality between the degree of canopy shading achieved with a specific AV module setup and the limitations in either net carbon exchange (NCER) or transpiration (T) rates. Under a similar degree of shading in DT and FH (i.e., 42–44% less than maximum incoming light), NCER was more restricted under the DT configuration. Conversely, under SAT, the limitations in light and NCER were nearly identical (around 19%). Canopy WUE did not increase in any of the module settings, except during the latter part of the HF period. When the sun's rays were nearly perpendicular to the modules, WUE significantly decreased under AV conditions, as T was clearly less constrained than NCER during those specific time windows. Prolonged AV configuration, as observed in the present study with FH, initiated certain low-light adaptation mechanisms, such as increased quantum yield and a slight delay in leaf senescence. Our work emphasizes the importance of careful AV design before installation in an existing vineyard to optimize light use and enhance desirable grape quality features (e.g., acidity preservation and limitation of sunburn damage).