Agrivoltaics improve grape quality in Mediterranean rainfed vineyards

Researchers from the University of Bari Aldo Moro in Italy Researchers have investigated the effects of photovoltaic-induced shading on vineyards of Primitivo, a traditional grape variety cultivated in the Apulia region. The study examines how partial shading from photovoltaic panels influences vine growth, microclimatic conditions, and grape production, providing insights into the potential integration of solar energy systems with viticulture.

“The objective is to assess whether agrivoltaic integration can mitigate the effects of high temperatures and water deficit, thereby improving grapevine adaptability in Mediterranean environments,” the scientists stated.

The experiment was conducted during the 2024 growing season in a commercial agrivoltaic vineyard located at the “Le Rene” solar farm in Laterza, southern Italy. The agrivoltaic system covered 8,812 m² with a photovoltaic capacity of 350 kW, while a nearby full-sun area served as the control. Three light treatments were established: full sun (FS, 100% irradiance), low shade (LS, approximately 95% irradiance between panel rows), and high shade (HS, approximately 5% irradiance beneath the panels).

Continuous monitoring of microclimatic parameters, including air and soil temperature, relative humidity, solar radiation, wind speed, and vapor pressure deficit, was performed using automated weather stations. Vine physiological responses were assessed throughout the growing season through measurements of stomatal conductance, leaf temperature, chlorophyll content, fluorescence, photosynthesis, transpiration, and water status.

Light quality and quantity were also characterized using spectral measurements of photosynthetically active radiation and the red-to-far-red ratio. Growth and morphological traits, including shoot development, leaf area, biomass accumulation, and stomatal characteristics, were evaluated through destructive sampling.

The study also investigated the impact of photovoltaic shading on spontaneous vegetation by comparing plant diversity and community composition beneath the panels and in the full-sun vineyard area using floristic surveys and diversity indices. At harvest, yield components and grape quality parameters were analyzed, including cluster number, cluster weight, berry composition, total soluble solids, pH, titratable acidity, polyphenol content, and anthocyanin profiles.

The analysis showed that the agrivoltaic system significantly modified the vineyard microclimate, vine physiology, growth, biodiversity, and grape quality. Shading reduced air temperature by approximately 0.5–1 C, increased relative humidity by up to 14%, and improved soil moisture compared with FS conditions, indicating a buffering effect against summer heat and drought stress. Physiological measurements revealed higher chlorophyll content, improved photochemical efficiency, and better water status under shaded conditions, particularly under HS, while LS maintained higher photosynthetic activity.

The altered light environment strongly affected vine morphology, with shaded vines producing longer shoots, larger leaves, thicker stems and petioles, and greater biomass accumulation than FS vines. Shading also increased stomatal density and modified stomatal characteristics, suggesting long-term physiological acclimation to reduced radiation. Floristic surveys showed that species richness beneath the photovoltaic panels was approximately twice that of the full-sun area, indicating that the agrivoltaic system created a more favourable microhabitat for spontaneous vegetation.

Yield components were positively affected by shading, with LS and HS treatments increasing cluster number, cluster weight, and yield per cane compared with FS vines. Although full-sun grapes reached slightly higher sugar concentrations, shaded grapes maintained adequate ripening parameters, higher acidity, and improved polyphenolic accumulation, especially under LS conditions.

Overall, the results demonstrate that agrivoltaic shading can enhance vine resilience, improve productivity, support biodiversity, and maintain grape quality in Mediterranean rainfed vineyards.

“These results indicate that agrivoltaic systems can influence vineyard functioning at multiple levels,” the researchers concluded. “However, long-term and multi-site evaluations are required to verify the responses in different climatic conditions, for more seasons and also with other fruit species.”

The research work can be found in “Agrivoltaics in Mediterranean viticulture: Impacts on physiology, yield andm biodiversity,” published in Scientia Horticulturae.