The Effect of Cultivation Techniques on the Antioxidant Properties and Phenolic Acid Content in the Roots of Five Sweet Potato (Ipomoea batatas L.) Cultivars Grown Under the Climatic and Soil Conditions of Southeastern Poland

This study confirmed that cultivation technologies, cultivar, and meteorological conditions significantly influenced the contents of ascorbic acid, total polyphenols, and phenolic acids in sweet potato roots. Ascorbic acid content ranged from 27.22 to 111.9 mg·100 g−1 DW, with the highest values recorded in the traditional cultivation system (TC), reaching 111.9 mg·100 g−1 DW in ‘Carmen Rubin’ and 111.4 mg·100 g−1 DW in ‘Beauregard’. In contrast, in the ‘Satsumo Imo’ cultivar grown under nonwoven fabric (WC), ascorbic acid content decreased to 49–58% of the values obtained in TC. Genetic factors strongly differentiated the contents of bioactive compounds. The ‘Purple’ cultivar showed the highest contents of total polyphenols (up to 963.5 mg·100 g−1 DW) and phenolic acids (17,067.42 mg·100 g−1 DW), whereas the lowest values were recorded in ‘Satsumo Imo’ (858.82–1225.89 mg·100 g−1 DW). Cultivation under polyethylene film (FC) increased and stabilized phenolic compounds. The ‘Carmen Rubin’ cultivar also exhibited high phenolic acid content (5332.04–5447.60 mg·100 g−1 DW), while ‘Beauregard’ was characterized by high stability of this trait (1535.93–1581.46 mg·100 g−1 DW). From a practical perspective, the results highlight the importance of appropriate cultivar selection and cultivation technology for obtaining raw material with high functional value. These findings may serve as a basis for developing agrotechnical recommendations aimed at producing sweet potatoes with enhanced nutritional and health-promoting qualities under the climatic and soil conditions of Poland.