Mulching, Closer Spacing, and Double Harvesting Increased Stevia Biomass Yield in Western North Carolina

Stevia (Stevia rebaudiana) is an increasingly popular natural sweetener that has been embraced by health conscious consumers around the world. Presently, most stevia is grown in China, India, and Vietnam. Now, however, several large corporations are producing stevia in the United States, including eastern North Carolina. Stevia as a commercial specialty crop may also present a unique economic opportunity for farmers in the mountains of western North Carolina (WNC) but it has not been evaluated in this region for commercial production. In this pilot study we used a randomized split-split plot design to investigate mulch types (black plastic, white plastic, and bare ground), in-row spacings (15, 30, and 46 cm in double rows with 30 cm between rows on the bed), and harvest times (single cutting and two cuttings) on yields of plant biomass and steviosides. The trial site was at the Mountain Research Station in Waynesville, NC. Rooted stevia plant plugs from cuttings of a commercially grown variety were transplanted in the field on 6 June 2014, on raised beds with drip-irrigation. For the two harvest treatment, the first cutting was on 22 July and the second was on 4 September. The single optimal harvest was done on different dates based on the plant development (30% bud stage) in each plot. Results indicated that biomass yields were significantly increased by applying plastic mulch and using the closest plant spacing compared to bare ground and the two wider plant spacings. No difference was detected between the two plastic types or between the two wider plant spacings. The double-cutting produced almost twice the biomass yield of the single harvest. The findings from this investigation indicate that plant spacing, mulching, and harvest times can significantly affect stevia biomass yield in WNC.