Osmocote incorporated in the potting substrate as the sole fertilizer source, seedling emergence and growth were hastened in treatment B, compared to that of control plants. This was likely the result of the acceleration of the four stages of seedling development due to Osmocote being incorporated in the substrate. The highest treatment rate E inhibited plant growth, indicating that the nutrient levels at this rate were actually above what the plants prefer or that soluble salt levels in the substrate at this fertilization rate may have been too high. Electrical conductivity of the substrate was not measured during the experiment. At harvest, seedlings in treatment B were still tallest; however, seedlings in treatment E demonstrated accelerated growth 12 weeks after sowing and attained a height similar to those in the control and treatment A.

Hershey and Paul (1983) and Raither and Frink (1989) both reported that leaching of nutrients from slow-release fertilizer was highest during the early part of the growing season. It would seem likely that plant growth in treatment E accelerated as Osmocote nutrients and/or soluble salts were leached from the substrate; thereby, reducing the nutrient levels in the substrate and promoting growth of the seedlings. Tall containers are used in the production of pawpaw seedlings in order to accommodate the strong taproot produced (Layne, 1996). Further studies to determine the effect of the placement of slow-release fertilizer application in containers (incorporated uniformly throughout the container versus top-dressing) on nutrient leaching and pawpaw seedling growth would be desirable. More frequent application of smaller quantities of slow-release fertilizer and placement in the container could also be helpful to reduce nutrient leaching; however, this would

result in additional labor costs. The Peters 20–20–20 plus soluble trace elements used in this study contained 3.9% ammoniacal N, 6.1% NO3-N, and 10.0% urea N, whereas Osmocote 14–14–14 contained 8.2% ammoniacal N, 5.8% NO3-N, and no urea. Ammonia and urea need to be converted to NO3 to be taken up by the plant. Further studies would be required to determine if pawpaw seedlings prefer a particular form of N and whether the N form in the fertilizer formulations used in these experiments affected pawpaw growth. The pH and soluble salt concentration of potting substrate that has been amended with high rates of Osmocote and the influence of these parameters on pawpaw growth in containers should also be examined further.

In conclusion, the slow-release fertilizer Osmocote 14–14–14 can be used effectively as a sole fertilizer source at treatment rate B (2.22 kg·m-3) or at a reduced rate of Osmocote, treatment rate A (0.81 kg·m-3), when supplemented with weekly applications of 500 mg·L-1 of Peters 20–20–20 liquid-feed fertilizer to enhance production of pawpaw seedlings in containers.

Arnold, M.A. and D.K. Struve. 1989. Growing green ash and red oak in CuCO3-treated containers increase root regeneration and shoot growth following transplant. J. Amer. Soc. Hort. Sci. 114:402–406.

Finneseth, C.L.H., D.R. Layne, and R.L. Geneve. 1998a. Morphological development of pawpaw [Asimina triloba (L.) Dunal] during seed germination and seedling emergence. HortScience 33:802–805.

Finneseth, C.L.H., D.R. Layne, and R.L. Geneve. 1998b. Requirements for seed germination in North American pawpaw [Asimina triloba (L.) Dunal]. Seed Sci. and Technol. 26:471–480.

Hershey, D.R. and J.L. Paul. 1983. Leaching-losses from pot chrysanthemums with controlled-release or liquid fertilization. Scientia Hort. 13:173–179.

Jones, S.C., R. N. Peterson, T. Turner, K.W. Pomper, and D. R. Layne. 1998. Pawpaw planting guide: Cultivars and nursery sources. KSU Pawpaw Ext. Bul. 001.

Layne, D.R. 1996. The pawpaw [Asimina triloba (L.) Dunal]: A new fruit crop for Kentucky and the United States. HortScience 31:777–784.

Mexal, J.G., R. Phillips, and R. Neumann. 1995. Mexican conifers' response to fertilizer type indicates difference between value and cost. Tree Planter's Notes 46:126–129.

Nelson, P.V. 1998. Greenhouse operation and management. Prentice-Hall, Inc. Upper Saddle River, NJ.

Pomper, K.W., D.R. Layne, and R.N. Peterson. 1999. The pawpaw regional variety trial, p. 353–357. In J. Janick (ed.). Perspectives on new crops and new uses. ASHS Press, Alexandria, Va.

Pomper, K.W., D.R. Layne, and S.C. Jones. 2002a. Incident irradiance and cupric hydroxide container treatment effects on early growth and development of container-grown pawpaw seedlings. J. Amer. Soc. Hort. Sci. 127:13–19.

Pomper, K.W., D.R. Layne, S.C. Jones, and M.G. Kwants. 2002b. Growth enhancement of container-grown pawpaw seedlings as influenced by media type, root-zone temperature, and fertilization regime. HortScience 37:329–333.

Raither, T.M. and C.R. Frink. 1989. Nitrate in runoff water from container grown juniper and Alberta spruce under different irrigation and N fertilization regimes. J. Environ. Hort. 7:32–35.

Ruter, J.M. 1994. Growth responses of four vigorous-rooted tree species in cupric hydroxide-treated containers. HortScience 29:1089.