engleski

Yield, nitrate and steviol content of stevia (Stevia rebaudiana Bertoni) leaves as affected by fertilization rate

Stevia (Stevia rebaudiana Bertoni) is cultivated for the sweet taste leaves, which are, after drying and grinding used as a substitute for artificial sweeteners. The aim of a study was to determine the effect of fertilizer dose on the fresh leaves yield, nitrate and steviol content. Plants were grown in a 5 L pots on the two types of acid soil (pH 4.0 and 5.0), which were different supplied with major nutrients. Five doses (0 to 1.6 g per plant) of mineral fertilizer Multi-Comp Base 14:13:20+2MgO+ME were applied. The highest dry leaves yields (30.28 and 30.98 g per plant) were achieved by application of 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 at unfertilized control. Increased fertilization intensity resulted with increased amount 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 determined. At the soil with pH 4.0, fertilization rate increasing, caused decreasing of N-NO3- amount 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 resulted in a higher nitrate amount in leaves than 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 higher ammonia amounts in leaves, 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 with economically effective yield of leaves which contained significant steviol amount.

Stevia rebaudiana Bertoni; fertilization; steviol

nije evidentirano