Effect of potassium hydrogel polymer on young grapevine growth and soil properties under controlled conditions

Potassium polyacrylates (SAPs) are hydrogels capable of retaining and gradually releasing water many times their own weight. When incorporated into soil, they can enhance soil water retention and offer a promising strategy to mitigate drought stress in viticulture. This study evaluated the effects of SAPs on the vegetative development and nutrient dynamics of potted young Vitis vinifera cv. Castelão vines in sandy soils under controlled drought conditions. Over two years, SAP-treated and untreated plants were exposed to varying periods of drought to better understand SAP–soil–grapevine interactions. SAP-treated plants showed accelerated phenological development in the second season, progressing faster under both full and deficit irrigation. They also exhibited increased shoot length and leaf area—with significant gains throughout the second year—and greater root biomass, with dry weight increases of 34.4 % and 35.5 % under well-watered and deficit irrigation, respectively. Additionally, SAPs enhanced irrigated water productivity (WP), which increased by 25.5 % under well-watered and 30.0 % under deficit conditions. Minor yet statistically significant differences in soil and leaf potassium and sodium levels were also observed, suggesting enhanced nutrient retention and uptake. Overall, SAPs improved grapevine growth at early stages of development and enhanced resource use efficiency, particularly under water-limited conditions. These findings underscore the potential of SAPs as a sustainable soil amendment in viticulture. Future research should focus on evaluating vine performance and soil health under field conditions to confirm these benefits at the vineyard scale.