Effects of Supplemental Irrigation and Hydrogel Application on the Enzymatic Darkening Susceptibility of Potato Tubers After Harvest and Storage

Increasing drought frequency associated with climate change highlights the need for effective water management to maintain potato tuber quality during production and storage. This study evaluated the effects of growing-season conditions, cultivar, supplemental irrigation, and hydrogel application on tuber oxidative potential and chlorogenic, ascorbic, and citric acid contents at harvest and after six months of storage. A three-year field experiment (2020–2022) was conducted using ten potato (Solanum tuberosum L.) cultivars under three cultivation treatments: control, supplemental irrigation, and hydrogel application. The year of the experiment, reflecting weather conditions during the growing season, was the factor that most strongly determined the analyzed quality parameters. The mean blackspot index was lowest in 2020 (0.207 AU475) and highest in 2021 (0.568 AU475), demonstrating substantial seasonal variation. Cultivar effects were also evident, with the highest mean values recorded for Bohun (0.449 AU475), Baltic Fire (0.418 AU475), Tajfun (0.416 AU475), and American Rose (0.415 AU475), whereas Ismena and Golden Marie had the lowest values (0.304 and 0.312 AU475, respectively). Chlorogenic acid was strongly positively correlated with oxidative potential (Spearman’s r = 0.757–0.852), whereas ascorbic and citric acids showed opposite associations. Both supplemental irrigation and hydrogel reduced susceptibility to enzymatic browning, but their effectiveness depended on growing-season conditions. Hydrogel application was most effective under the greatest water deficit, whereas its effect was less pronounced in wetter seasons. Overall, the results demonstrate that weather conditions during the growing season were the primary determinant of tuber quality, while cultivar and water-management practices modified the response. Hydrogel application may therefore provide a useful strategy for reducing drought-related quality deterioration and improving the storage stability of potato tubers under water-limited conditions.