Irrigation Practice in Cultivation of Stevia rebaudiana Bertoni in Cooler Climates—Case Study in Poland

Stevia rebaudiana Bertoni originated in South America, but has gained popularity due to the concentration of sweet steviol glycosides present in its leaves. Stevia is also currently grown on other continents in many countries characterised with warm climate. This research aimed to determine whether different irrigation practices might have a significant influence on the yield and composition of the leaves of stevia plants grown in Poland, in cooler climate than native regions for stevia plants. Stevia plants were grown with four different irrigation regimes: irrigation twice a week, irrigation once a week, irrigation only during times of the drought and not irrigated at all. It was determined that different irrigation regimes have substantial effects on the yield, biometric characteristics and chemical composition of stevia leaves, but none of the irrigation regimes were clearly supreme to the others. Yield of stevia plants that were irrigated once a week or only during the drought times was the highest (2.42&ndash:2.58 kg per square meter). Stevia plants that were not irrigated were characterised with the lowest height and lateral width (47.61 and 25.35 cm). Leaves of un-irrigated stevia contained the greatest dry mass content (30.47%) and highest concentration of phenolic compounds (337.88 mg per 100 g of fresh stevia leaves). Stevia plants that were irrigated once or twice a week were characterised with a lower concentration of chlorophylls or carotenoids at the time of the harvest (1.20&ndash:1.24 and 2.54&ndash:2.58 mg per gram of fresh stevia leaves), but stevia plants that were not irrigated contained a greater amount of chlorophyll and carotenoids (1.58 and 3.17 mg per gram of fresh stevia leaves).