Growth and Phytochemical Production of Wild-Simulated Ginseng in Response to Processed Red Clay and Rice Husk

This study investigated the effects of environmentally friendly soil amendments—processed red clay (PRC) and rice husk (RH)—on early establishment, growth characteristics, phytochemical accumulation, and soil chemical properties in wild-simulated ginseng (WSG; Panax ginseng C.A. Meyer) cultivated under forest conditions. PRC was produced through alkali-assisted thermal processing to improve material homogeneity and enhance plant-available mineral components, particularly silicon. We hypothesized that the combined application of PRC and RH would improve soil chemical conditions and thereby support WSG growth and phytochemical accumulation under low-input cultivation systems. Four treatments were evaluated in a randomized complete block design with four replicates: non-treated control (NMNF), PRC alone (NMPRC), RH alone (RHNF), and combined PRC and RH (RHPRC). Growth responses were assessed in one-year-old and seven-year-old WSG, including germination rate, seedling vigor index, growth traits, photosynthetic pigment composition, total polyphenol content, ginsenoside profiles, and soil chemical properties. The RHPRC treatment significantly increased germination rate and seedling vigor compared to the non-treated control and showed consistently greater biomass accumulation across cultivation stages. RH application was primarily associated with improved early establishment and increased total polyphenol content, particularly during the early growth stage, whereas PRC application was associated with enhanced root development and age-dependent increases in selected ginsenosides. Soil analyses indicated that PRC application increased available phosphorus and exchangeable cation contents, with the most stable improvements observed under combined PRC and RH treatment. Overall, the results indicate that integrated mineral–organic soil management using PRC and RH can improve soil chemical propertise and support long-term growth and phytochemical accumulation in WSG cultivated under forest conditions. This approach offers a practical, low-input strategy for enhancing the sustainability of WSG cultivation while reducing reliance on synthetic fertilizers.