Sweetpotato growth and yield from plug transplants of different volumes, planted intact or without roots

Single-node leafy cuttings of sweetpotato [Ipomoea batatas (L.) Lam. cv. Beniazuma] plants can be used to produce low-cost, pathogen-free sweetpotato plug transplants. This study was conducted to determine the effects of plug volume and root removal on sweetpotato growth and yield after planting in the field. The yield and growth of sweetpotato plants from transplants with 4 to 6 unfolded leaves (about 0.14-m shoot length) produced in 55- or 35-mL multicell plug trays, then planted intact or without roots were compared with a control treatment of unrooted conventional cuttings (about 0.3-m-long terminal vine cutting with 7 to 8 unfolded leaves). The plug transplants were grown from single node leafy cuttings under artificial light. Intact plug transplants (35 or 55 mL) produced 39 to 40 Mg [ha.sup.-1] of storage roots 128 d after planting in the field, 11 to 12 Mg [ha.sup.-1] greater than the control treatment. After 128 d of field growth, plug transplants (35 mL, with roots) gave a percent harvest index of 79%, 7% greater than the control. The maximum length and diameter of storage roots were, respectively, 271 and 68 mm when plug transplants were used (35 mL, with roots), and were, respectively, 58 mm longer and 18 mm wider than the control. Overall, growth and yield from plug transplants were significantly higher than from conventional cuttings, regardless of the plug volume or root removal. Plug transplants with intact roots produced greater growth and yield regardless of plug volume than did plug transplants without roots.