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<p><i>Panax ginseng</i> (C.A. Meyer) is an important medicinal plant cultivated under heavy shade, and stable production of high-quality roots requires appropriate nutrient management. Nitrogen (N) fertilization remains difficult to optimize because excessive N can promote shoot growth disproportionately, impair root development, and increase the risk of root quality deterioration and soil-related problems. We evaluated the response of two-year-old <i>P</i>. <i>ginseng</i> plants to four basal N application rates (0, 2, 4, and 8&#xa0;g N m<sup>− 2</sup>) under typical shaded cultivation. Seasonal changes in SPAD value, a relative chlorophyll index measured with a SPAD meter, and leaf area were monitored, net photosynthetic rate was measured under low light, and shoot and root dry matter production together with tissue carbon (C) and N accumulation were determined at harvest. Higher N application maintained higher SPAD values, prolonged leaf area retention, and increased net photosynthetic rate, indicating improved leaf function under shade. Shoot biomass and shoot C and N accumulation increased approximately linearly with N supply. In contrast, root dry weight and root C and N accumulation showed a saturating response, with little additional gain at the highest N level. These results suggest that although increased N enhances assimilatory capacity, root accumulation responds less proportionally at higher N supply. Based on the balance between leaf assimilation and root accumulation, the practical optimum basal N range for two-year-old ginseng under shaded cultivation was estimated to be 6–8&#xa0;g N m<sup>− 2</sup>. These findings provide a physiological basis for N management in <i>P</i>. <i>ginseng</i> as a medicinal root crop.</p> Graphical abstract <p></p>

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Optimizing nitrogen fertilization for shaded cultivation of the medicinal plant Panax ginseng: implications for photosynthesis, root growth, and carbon accumulation in two-year-old plants

  • 期刊论文

  • 发表日期：

    2026年6月16日

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  • Shingo Matsumoto,
  • Junko Kasuga,
  • Masayuki Kadowaki,
  • Michiho Ito

摘要

Panax ginseng (C.A. Meyer) is an important medicinal plant cultivated under heavy shade, and stable production of high-quality roots requires appropriate nutrient management. Nitrogen (N) fertilization remains difficult to optimize because excessive N can promote shoot growth disproportionately, impair root development, and increase the risk of root quality deterioration and soil-related problems. We evaluated the response of two-year-old P. ginseng plants to four basal N application rates (0, 2, 4, and 8 g N m− 2) under typical shaded cultivation. Seasonal changes in SPAD value, a relative chlorophyll index measured with a SPAD meter, and leaf area were monitored, net photosynthetic rate was measured under low light, and shoot and root dry matter production together with tissue carbon (C) and N accumulation were determined at harvest. Higher N application maintained higher SPAD values, prolonged leaf area retention, and increased net photosynthetic rate, indicating improved leaf function under shade. Shoot biomass and shoot C and N accumulation increased approximately linearly with N supply. In contrast, root dry weight and root C and N accumulation showed a saturating response, with little additional gain at the highest N level. These results suggest that although increased N enhances assimilatory capacity, root accumulation responds less proportionally at higher N supply. Based on the balance between leaf assimilation and root accumulation, the practical optimum basal N range for two-year-old ginseng under shaded cultivation was estimated to be 6–8 g N m− 2. These findings provide a physiological basis for N management in P. ginseng as a medicinal root crop.

Graphical abstract