A series of experiments investigated the effects of increasing phosphate–phosphorus (P) concentrations on the growth and development of four horticultural species. In experiment 1, petunia [Petunia atkinsiana (Sweet) D. Don ex W.H. Baxter] plants were grown using eight P concentrations, and we found that the upper bound for plant growth was at 8.72–9.08 mg·L−1 P, whereas concentrations ≤2.5 mg·L−1 P caused P deficiency symptoms. Experiment 2 investigated P growth response in two cultivars each of New Guinea impatiens (Impatiens hawkeri W. Bull) and vinca [Catharanthus roseus (L.) G. Don]. Growth for these plants was maximized with 6.43–12.42 mg·L−1 P. In experiment 3, ornamental peppers (Capsicum annuum L. ‘Tango Red’) were given an initial concentration of P for 6 weeks and then switched to 0 mg·L−1 P to observe whether plants could be supplied with sufficient levels of P, and finished without P to keep them compact. Plants switched to restricted P began developing P deficiency symptoms within 3 weeks; however, restricting P successfully limited plant growth. These experiments indicated that current P fertilization regimens exceed the P requirements of these bedding plants, and depending on species, concentrations of 5–15 mg·L−1 P maximize growth.
We are grateful for the funding support provided by the Fred C. Gloeckner Foundation, the USDA Floriculture and Nursery Research Initiative, American Floral Endowment Altman Family Scholarship, and The Garden Club of America. We would also like to express our gratitude to Dümmen Orange for providing cuttings and for peat moss provided by Sun Gro Horticulture.
HansenC.W.NielsenK.L.2001Reduced phosphorus availability as a method to reduce chemical growth regulation and to improve plant quality p. 314–315. In: W.J. Horst M.K. Schenk A. Bürkert N. Claassen H. Flessa W.B. Frommer H. Goldbach H. Olfs V. Römheld B. Sattelmacher U. Schmidhalter S. Schubert N. von Wirén and L. Wittenmayer (eds.). Plant nutrition - Food security and sustainability of agro-ecosystems. Springer Dordrecht The Netherlands
HenryJ.B.2017Beneficial and adverse effects of low phosphorus fertilization of floriculture species. MS Thesis N.C. State Univ. Raleigh