Optimizing Biomass and Steviol Glycoside Yield in Hydroponically Grown Stevia ( Stevia rebaudiana Bertoni) with Ammonium Nitrate and 6-Benzylaminopurine Concentrations

This two-year (2016–2017) study aims to fill in the gaps in our knowledge by looking at how hydroponic cultivation conditions affect stevia's growth, figuring out the best way to use nitrogen fertilizer and BAP to get the best yield and quality, and figuring out how well plants do in terms of stevioside and rebaudioside A content. The experiment was conducted based on a fully factorial layout in a completely randomized design with three replications. The treatments included five levels of ammonium nitrate (75, 150, 225, 300, and 375 mg/L) and four concentrations of 6-benzylaminopurine (BAP) (0, 75, 150, and 225 μM). The results showed that nitrogen use, which varied depending on the amount of BAP used, significantly influenced the growth, development, and economic performance of stevia. To determine the best treatment combination, it is important to consider the plant's economic performance, which is the dry weight of the leaves. The optimal treatment combination involved the use of 75 μM BAP and 75 mg/L of ammonium nitrate. This treatment combination produced the highest amounts of stevioside (2.17 g/plant) and rebaudioside A (0.67 g/plant), representing an increase of approximately 48% compared to the use of 75 mg/L of ammonium nitrate alone. Assuming a plant density of 100,000 plants per hectare, the application of 89 kg N/ha would result in the highest productivity of stevioside (217 kg/ha) and rebaudioside A (67 kg/ha). Higher nitrogen levels increased the proportion of leaf biomass in the plant but reduced the photosynthetic efficiency of the leaves. The results also revealed that a decrease in temperature and photoperiod can negatively impact the growth of stevia plants. The use of hydroponics allowed for a reduced use of nitrogen, making it an environmentally friendly option.