Biological and agrotechnical bases of stevia (<i>Stevia rebaudiana</i> bertoni) cultivation in the Forest-steppe and the Steppe of Ukraine
The necessity of growing stevia in the Forest-Steppe and the Ukrainian Steppe has been theoretically substantiated and practically proved. Breeding methods and basic elements of stevia growing technology are developed on the basis of the plant biological characteristics, its adaptive potential and varieties analysis. Research results. The recommended technology has ensured the maximum implementation of the biological potential of stevia plants, which is manifested in more intensive growth and development of plants, significantly increased the yield of green mass and dry leaves compared with the control, respectively, by 6.2 and 1.1 t/ha. In order to obtain stevia dry leaves yield at the level of 3.5-4.0 t/ha it is recommended to sow the new generation varieties of domestic breeding: Halyna, Maryna, Kateryna; stevia propagation method was proposed (Patent No. 119472, 2017). Over the years of testing, the annual economic effect amounted to 585.1 thousand UAH. Conclusions. 1. The theoretical basis of the recommended stevia cultivation technology is the determination of the patterns of leaf mass formation, photosynthetic potential and the net productivity of photosynthesis depending on the varietal composition of the elements of growing technology and weather conditions of the growing season. 2. To get a yield of stevia dry leaves at the level of 3.5-4.0 t/ha it is recommended: - to grow stevia in the regions where the annual amount of precipitation year is 460-560 mm, including 322-460 mm for the vegetation period, the moisture content in 100 cm soil layer - 150-180 mm, the amount of temperature during the period of active vegetation - 2450-2800 °С, SТC - 0.8-1.3; - to sow varieties of domestic breeding: Berehynya, Slavutych, Halyna, Maryna, Kateryna. 3. Growing stevia by seedlings method should be carried out on May 20-30 in a 70x16 cm pattern.