Effect of Fertilization Levels on Growth and Physiological Characteristics of Containerized Seedlings of Vaccinium oldhamii

<i>Vaccinium oldhamii</i>, a blueberry species native to Korea, is a deciduous shrub in the Ericaceae family. Its fruit possesses various pharmacological properties, including anti-inflammatory effects and potential for treating osteoporosis. This study evaluated the effects of five fertilization concentration levels using Multifeed 20 (N:P:K = 20:20:20) on the growth and physiological characteristics of one-year-old <i>V. oldhamii</i> container seedlings. Treatments included 0 g·L^-1 (control), 0.5, 1.0, 1.5, and 2.0 g·L^-1. Increases in stem thickness, root length, and total dry weight were observed in the control, 0.5, 1.0, and 1.5 g·L^-1 treatments, whereas growth declined at 2.0 g·L^-1. Mortality rates exceeded 15% at concentrations above 1.0 g·L^-1. Photosynthetic capacity and chlorophyll content increased with fertilization. However, while growth improved with increasing fertilizer up to a certain level, it declined at the highest concentration. A fertilization rate of 0.5 g·L^-1 proved to be the most economically and environmentally efficient for producing healthy seedlings. This study provides the first fertilization threshold for <i>V. oldhamii</i>, offering practical guidance for nursery production and forming a foundation for future domestication strategies.