Agronomic Evaluation of a 5-Node Seedling Standard for Fresh-Market Sweet Potato ‘Beniharuka’ Production

The need for mechanization of sweet potato production remains a critical challenge. Furthermore, automated transplanting using large-scale machinery remains semi-automated and presents an operational challenge. Here, we evaluated the agronomic suitability of a short, 5-node seedling standard for improving mechanical adaptability without compromising plant productivity and root quality. The growth characteristics, biomass accumulation, carbon (C) and nitrogen (N) contents, post-transplant survival, and storage root yields of 5-node seedlings and conventional 7-node seedlings of the premium fresh-market cultivar ‘Beniharuka’ were compared. The 5-node seedlings exhibited lower initial dry masses and smaller leaf areas. However, the 5-node standard significantly reduced the stem bending index and reduced the percentage of seedlings that were mechanically unsuitable for transplanting (bending angle ≥ 40°). The post-transplant survival rate of the 5-node seedlings decreased by approximately 20% compared with that of the conventional control (p = 0.053). Although this difference was marginally non-significant, it represents a substantial biological reduction in early field establishment. However, the comparable final yield components indicated that the cultivar ‘Beniharuka’ exhibited comparable yield performance under the tested conditions. While addressing this survival challenge through targeted agronomic management is essential for practical implementation, the 5-node standard represents a promising morphological strategy to improve compatibility with automated transplanters in fresh-market sweet potato production.