The effects of different nitrogen doses on the some yield and quality properties of sugar plant (Stevia rebaudiana Bertoni)

In this thesis, effects of different nitrogen doses on yield (days for flowering, plant height, number of stem, green herb yield, green leaf yield, drog herb yield, drog leaf yield, leaf/stem rate, drog leaf/stem rate) and quality (steviol glycoside content) of Stevia rebaudiana plant were investigated. The experiment was carried out in randomized plots design with four replications during three years (2011-2012-2013) at the Field Crops Research and Application fields of Agriculture Faculty, Akdeniz University. Row spacing and intra-row spacing were 65 cm and 45 cm, respectively. For nitrogen treatments, ammonium nitrate fertilizer (33% N) was applied to each experimental plot after planting the seedlings for various N doses (0, 5, 10, 15 and 20 kg/da N). Also, 8 kg/da potassium and phosphate were applied to the plots just before the planting. According to three years average results, it can be underlined that the earliest flowering was observed on day 162 in 0 of N dose in terms of the number of days to flowering. The highest plant height was determined from 10 and 15 kg/da N doses as 121 cm. While the highest number of main stem was observed from 10 kg/da N dose as 19, the highest fresh herb yield was obtained from 15 kg/da N dose as 2675.3 kg/da. Furthermore, the highest fresh leaf yield was found to be 1326.58 kg/da from 10 kg/da N dose and the highest dry herb yield was determined as 750 kg/da from 15 kg/da N dose. The highest dry leaf yield was obtained from 10 kg/da N dose as 381.75 kg/da. On the other hand, the best leaf/stem rate was 1.09 in control group. In terms of steviol glycosides, the highest ratio of stevioside and rebaudioside A were determined from 5 kg/da N dose as 12.40 and 5.65 respectively. In addition the highest ratio of rebaudioside A was obtained as 5.65 from 5 kg/da N dose. As a result, 10 kg/da N dose is suitable for cultivation of sugar plant and this plant can be grown as perennial plant in Antalya conditions.