Decreasing Phosphorus Fertility to Reduce Sweetpotato Root Growth During Container-grown Transplant Production

Sweetpotato [Ipomoea batatas (L.) Lam.], grown as an edible ornamental, is propagated in home gardens using locally purchased transplants. However, vigorous growth of sweetpotato limits the period of transplant salability due to root confinement. The objective of the experiment was to evaluate reductions in phosphorus (P) fertility to slow transplant root growth and extend the period of salability. Cuttings were planted into containers and fertilized at 0, 5 (0.0007), 10 (0.0012), 15 (0.0020), 20 (0.0024), and 31 mg P.L −1 (0.0040 oz P.gal−1) using a modified Hoagland solution. All transplants fertilized at ≥5 mg P.L −1 increased in shoot length, color, and biomass during the first four weeks after planting (WAP) but declined thereafter. Transplant roots fertilized at ≥5 mg P.L −1 (0.0007 oz P.gal−1) increased in total length, surface area, and volume throughout the six-week production cycle. However, P fertility <15 mg.L -1 (0.0020 oz P.gal−1) resulted in narrower storage roots with lower root volumes. Reducing P fertility from 31 (0.0040 oz P.gal−1) to 5 mg L −1 (0.0007 oz P.gal−1) did not sufficiently slow transplant rooting to prevent roots from reaching container walls to extend the period of salability. Index words: root length, root diameter, root biomass, and root architecture. Species used in this study: Sweetpotato [Ipomoea batatas (L.) Lam.].