Nutrient and biomass dynamics for dual-organ yield in turmeric (Curcuma longa L.)

In China, Curcuma longa L. is primarily cultivated for its underground parts-rhizomes (commonly known as turmeric) and tubers (Yujin), with the latter holding greater market value. However, current cultivation practices in China remain largely traditional, lacking scientific optimization in nutrient management, growth cycle alignment, or soil fertility strategies. This study aims to establish a scientific foundation for precision fertilization by investigating the dynamic patterns of dry matter accumulation and nutrient distribution in multiple plant organs throughout the growth cycle.

The experiment was conducted in Shuangliu, Sichuan Province, a key production area for Curcuma longa in China. From 55 to 209 days after planting (DAP), nine sampling points representing different phenological stages were selected. At each stage, we systematically monitored the accumulation of dry matter and the distribution of nine essential nutrient elements-nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn)-across five plant organs: leaves, stems, rhizomes, tubers, and roots.

The total dry matter accumulation in Curcuma longa followed a typical S-shaped curve, reaching its peak at 195 DAP. Resource allocation patterns varied across four distinct growth stages. Before October (0-111 DAP), the aboveground parts dominated, with leaves and stems comprising 62.73% to 79.30% of the total dry mass. After October (111-195 DAP), underground development intensified, with priority given to the rhizomes and tubers. By late December (195 DAP), dry matter in the tubers peaked, and by early January (209 DAP), over 70% of the total dry mass was allocated below ground. Nutrient uptake also showed distinct temporal patterns. Total accumulation of nutrients in mature plants was as follows: K (1,492.39 mg), N (1,198.81 mg), P (396.98 mg), Ca (339.51 mg), Mg (210.63 mg), Fe (15.17 mg), Zn (1.15 mg), Mn (0.69 mg), and Cu (0.25 mg). The relative nutrient demand ranked as follows: K > N > P (macronutrients), Ca > Mg (secondary nutrients), and Fe > Zn > Mn > Cu (micronutrients).

The growth and development of Curcuma longa depend on sufficient uptake of potassium and nitrogen, moderate amounts of phosphorus, calcium, and magnesium, and trace amounts of iron, zinc, manganese, and copper-of which potassium is required in the greatest quantity. These findings highlight the importance of adopting a stage-specific fertilization strategy to align with the plant's shifting nutrient demands throughout its life cycle.