Effects of New Synthetic and Organic Hydrogel Soil Application on Physiology, Fruit Composition, and Wine Quality of Water‐Stressed Potted Grapevines

Background and Aims Climate change poses increasing issues to the rapid and successful establishment of new vineyards. In this study, conducted over two consecutive seasons on potted vines, we evaluated the effects of a synthetic potassium polyacrylate hydrogel (WS‐SH) and an organic‐based hydrogel (WS‐OH), both applied at transplanting, on vine water status, productivity, and fruit and wine composition, under progressive water deficit. These treatments were compared with a water‐stressed control (WS‐C) and a fully irrigated reference (WW‐C). Methods and Results In both years, WS‐SH and WS‐OH treatments delayed the decline in predawn water potential by several days and improved leaf gas exchange under limited irrigation. This led to increased leaf area and overall vine vigor. By the end of the second year, WS‐OH had greater root system development compared to all other water‐stressed treatments (+17% than WS‐C), while WS‐SH favored dry matter allocation toward aboveground organs (+17.6%). As a result, both WS‐SH and WS‐OH vines maintained yields comparable to WW‐C, whereas WS‐C showed a 33% yield reduction. Due to higher crop loads, WS‐SH and WS‐OH vines had lower leaf‐to‐fruit ratios than WS‐C (−0.116 m 2 /kg and −0.147 m 2 /kg, respectively), resulting in reduced grape sugar content (−1.8 and −1.6°Brix, respectively), anthocyanins (−48% and −51%, respectively), and phenolics (−21% and −23%, respectively). Wines produced at the end of the second season reflected this composition, showing significantly lower alcohol content (−1.11% v/v and −1.05% v/v, respectively), phenolic levels, and chromatic traits. Conclusions Our results demonstrate that hydrogels applied at transplanting can enhance vine tolerance to water stress and increase yield in the first productive season, in exchange for a reduction in sugar and anthocyanin contents in grapes. Significance of the Study Hydrogels could represent valuable tools to increase vineyard tolerance to summer stresses after transplanting. No substantial differences were observed between the effects of the synthetic and organic hydrogels, highlighting the potential of organic formulations as a sustainable and effective strategy to improve vineyard resilience to summer drought conditions. These results should be confirmed under operational conditions through field experiments.