Assessment of Sweetpotato Clones and Stem Cutting Planting Orientations in Organic Sweetpotato Production
Alyssa Woodard, MS Seminar
Under the direction of Dr. Jonathan Schultheis and Dr. David Suchoff
Friday, September 16, 2022 @ 1:00pm
121 Kilgore Hall / Zoom

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Meeting ID: 930 6417 0468
Passcode: 003705

Summary:
In North Carolina (NC), organic sweetpotato production has more than doubled in area harvested from 2011 to 2019 (USDA NASS, 2012, 2020). However, research and outreach efforts have not matched this growing market. Consequently, information to help growers make research-based decisions regarding best practices for organic sweetpotato yield and quality is limited. Therefore we conducted two studies aimed to determine optimal management practices that address the needs of organic sweetpotato producers.

In the first study, we conducted on-farm field trials during the 2020 and 2021 growing seasons to evaluate 13 sweetpotato clones for their fit and productivity in an organic production system. Data collected included vine and internode measurements, growth habit ratings, and yield. In addition, roots were cured and stored for eight months following harvest. Roots were sampled throughout this time to observe changes to starch and sugar composition during curing and throughout storage. Findings from this study indicate that the majority of clones had a moderate to spreading growth habit, however, ‘Monaco’ and ‘NC 10-0433’ had more upright growth, with short internodes and the shortest vine lengths. Clones with this architecture may be of particular interest for weed management strategies in organic production systems. Many clones yielded statistically similar to ‘Covington,’ the NC standard, however, practically some clones yielded as low as 52% to 65% of ‘Covington.’ Delaying harvest from ~105 to ~126 days after planting significantly increased yield for some clones, with more clones seeing this benefit in 2020 than 2021. Carbohydrate contents were affected by curing and long term storage, with clones differing in both carbohydrate composition and their responses to curing and storage. These findings indicate potential differences in eating quality and storage stability.

The second study evaluated the planting orientations of sweetpotato stem cuttings. ‘Monaco’ stem cuttings were planted with different orientations using a standard transplanter (vertical), a standard transplanter with a sleeve attachment (portion of cutting horizontal), and a horizontal transplanter. In addition, two stem cutting lengths (25 cm and 38 cm) and two harvest times (~108 days and ~126 days) were investigated. In 2020, marketable yields were highest when planted horizontally, lowest when planted vertically, and intermediate with the sleeve attachment. Marketable yields were 16% higher when planted horizontally as compared to vertical. However, in 2021, there were no significant differences in marketable yield when comparing planting orientations. Averaged over both years, yields of USDA No. 1 roots were 18% higher when planted horizontally compared to vertical. Regardless of planting orientation, delaying harvest until ~126 days is recommended to increase yields for ‘Monaco.’ In addition, No. 1 roots from the horizontal orientation were longer than the sleeve or vertical orientations, by 1.7 cm and 1.9 cm, respectively. Results of this study suggest shifting production practices to use horizontal transplanters could increase sweetpotato crop yields and improve land use efficiency.