Yield, nitrate and steviol content of Stevia (Stevia rebaudiana Bertoni) leaves as affected by fertilization rate
2012
Novak, B. | Benko, B. | Spicnagel, A.M. | Fabek, S. | Mesic, M.
Stevia (Stevia rebaudiana Bertoni) is cultivated for the sweet taste of its leaves, which are, after drying and grinding used as a substitute for artificial sweeteners. The aim of this study was to determine the effect of fertilizer dose on the fresh leaves yield, nitrate and steviol content. Plants were grown in 5-L pots on the two types of acid soil (pH 4.0 and 5.0), which were supplied with different major nutrients. Five doses (0 to 1.6 g per plant) of mineral fertilizer Multi-Comp Base 14:13:20 (N:P:K)+2MgO+microelements were applied. The highest dry leaves yield (30.28 and 30.98 g per plant) was achieved by applying 1.6 and 0.8 g of fertilizer on soil with pH 4.0 and 5.0, respectively. These yields were 21.6, and 39.8% higher than the yield achieved under unfertilized control. Increased fertilization intensity resulted in higher amounts of total nitrogen in stevia leaves. Depending on the soil type, amounts between 14.32 and 20.61 g per kg of dry matter (DM) were obtained. At the soil with pH 4.0, higher fertilization rates decreased the amount of N-NO3- in leaves from 18.16 to 10.05 mg per kg DM. At pH 5.0, only the fertilization with 1.6 g per plant increased the amount of nitrate in leaves compared to the unfertilized control (14.14 compared to 13.69 mg per kg DM). The amount of N-NH4+ in the leaves showed the opposite trend. Increased fertilization rates resulted with an increased accumulation of ammonia in leaves, passing from 214.55 to 387.83 mg per kg DM. Average glycosides content was between 42.0 and 45.7 mg SE (steviol equivalents) per g of dry leaves. Stevia cultivation on the soil with higher pH value and medium fertilization rate resulted in economically profitable yield of leaves which contained significant steviol amount.
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