Horizontal Planting Orientation Can Improve Yield in Organically Grown Sweetpotato

Sweetpotato [Ipomoea batatas (L.) Lam.] is one of North Carolina's (USA) most important organic commodity crops; however, yields tend to be less when compared with conventionally produced sweetpotato. Standard field establishment uses unrooted stem cuttings that are transplanted vertically in the soil. Producers in other countries typi-cally use other planting orientations, including cuttings transplanted horizontally. Empiri-cal evidence from North Carolina, USA, sweetpotato producers suggests that a horizontal orientation may improve yields. An organically managed field study using 'Monaco' sweetpotato was conducted in 2020 and 2021 in Bailey, NC, USA. The study evaluated stem cutting planting orientations (vertical, sleeve, horizontal), stem cutting length (25 cm and 38 cm), and harvest time (early or late) in a full-factorial randomized complete block design. In 2020, marketable yields were 16% greater for the horizontal orientation com-pared with the vertical orientation, with intermediate yields using the sleeve attachment. However, in 2021, there were no differences in marketable yield among planting orienta-tions. In both years, US No. 1-grade yields were significantly greater when cuttings were planted horizontally compared with vertically, with an average increase of 18%. Delaying har-vest until similar to 126 days is recommended to increase yields for 'Monaco', regardless of planting orientation. This study provides evidence that a horizontal planting orientation could increase premium root yields and improve land-use efficiency for organically produced sweetpotatoes.