Determination of Optimal Soil Moisture Depletion Level for Stevia (Stevia Rebaudiana Bertoni) at Wondo Genet, South Ethiopia

Abstract

The study was conducted based on the objective to evaluate the optimal soil moisture depletion level of stevia (Stevia rebaudiana Bertoni). Six levels of soil moisture depletion (20, 30, 40, 50, 60, and 100%) with four replications were used in a randomized complete block design. Different levels of total available water depletion significantly (p<0.05) affected all recorded yield and yield components. Significantly highest plant height, fresh and dry leaf weight, fresh and dry stem weight, aboveground fresh and dry biomass, and water productivity were obtained as stevia was irrigated below 40% TAW depletion level. However, water productivity was decreased both at higher and lower depletion levels and higher was at 30 and 40% depletion levels. The pooled mean revealed that irrigating stevia under different soil moisture depletion levels had a significant (p<0.05) effect on fresh leaf weight, fresh stem weight, dry stem weight, fresh biomass, and water productivity. Moreover, plant height, dry leaf weight, and dry biomass of stevia were also highly significantly (p<0.01) affected due to different soil moisture depletion levels. The maximum plant height (23.95 cm), fresh leaf weight (3300.3 kg/ha), fresh stem weight (1213.3 kg/ha), fresh biomass (4513.6 kg/ha) and water productivity (1.92 kg/m3) were recorded at 30% TAW. Moreover, the maximum dry leaf weight (1155.8 kg/ha), dry stem weight (869.0 kg/ha) and dry aboveground biomass (2024.7 kg/ha) were recorded at 40% TAW. On the other hand, the minimum growth, yield and yield component, and water productivity were recorded at 100% TAW. The current study revealed that irrigating stevia after 40% of the total available water in the soil depleted could be practiced in the study area and similar agroecology and soil type as the wider irrigation interval could be achieved without significantly affecting yield and water productivity.