Yield and growth rate of sweet potatoes as influenced by transplant orientation

Field experiments were conducted at Fayetteville and Knoxville, Tennessee to (1) provide information on seasonal growth patterns and growth characteristics of 'Centennial' and 'Jewel' sweet potatoes, (2) compare growth characteristics and marketable yield between vertically and horizontally orienting slips of these cultivars at planting, and (3) determine alternate methods for measuring leaf area of sweet potato plants. Treatments consisted of 'Centennial' and 'Jewel' each having vertical and horizontal slip orientations. Treatments were arranged in a split plot design and were replicated eight times. Vertically oriented 'Centennial' plants produced a higher per-centage of number one grade roots and a greater marketable yield than horizontally oriented plants of the same cultivar. Plant orientation appeared to have little or no effect on grade or marketable yield of 'Jewel.' Generally, horizontally oriented slips of 'Centennial' and ver-tically oriented slips of 'Jewel' maintained larger leaf areas, more roots per plant and greater root dry matter accumulation than the other planting orientation of the respective cultivar. Dry matter accumulation by both cultivars began as early as 30 days from planting and by 60 days one-third of the total root dry matter accumulation for the season had occurred. An inverse relation-ship was found between stem growth rate and root growth rate; as one increased the other slowed. Horizontally oriented slips of both culti-vars had larger diameter developing roots at most harvest dates than vertically oriented plants. No difference in plant survival between slip orientations was observed. Relatively strong correlations were obtained between root dry matter accumulation and mean developing root diameter and between root dry matter accumulation and stem dry weight for each cultivar. For both cultivars, weaker correlations were found between number of devel-oping roots per plant and root dry matter accumulation and between num-ber of developing roots and mean developing root diameter. Methods based on the midvein length and fresh weight were found to correlate highly with an automatic area meter (Hayashi Denko, Model AAM-5) for determing leaf area.