Nutrient dynamics during the growth period of Epimedium pubescens and its impact on growth and Icariin-Flavonoids composition

Comprehending nutrient content fluctuations across growth cycles is vital for optimizing fertilization to boost medicinal plant yield and quality in artificial cultivation. Nutrient dynamics and their impact on Epimedium pubescens' growth throughout its annual cycle remain unclear. Using two-year-old E. pubescens, we collected ten whole-plant samples at each of the five key growth stages within a year, analyzing biomass, Icariin-Flavonoids, nitrogen (N), phosphorus (P) and potassium (K) content in plant parts, and soil nutrients. Variance Partitioning Analysis (VPA) quantified NPK's importance to biomass and Icariin-Flavonoids via contribution rates. Structural Equation Model (SEM) explored relationships between soil nutrients, plant nutrient content, and biomass/Icariin-Flavonoids via path coefficients and significance. The results indicate that the nutrient demand of E. pubescens during its growth cycle follows the order of N > K > P. VPA, SEM highlighted N's key role, soil N affected plant N in Feb (-0.537, p＜0.001), Jul (0.410, p＜0.001); Plant N is crucial for biomass (Apr: 23.7 %, Jul: 54.8 %) and Icariin-Flavonoids (Apr: 27.2 %, the next Feb: 30.5 %). Soil P impacted plant P in Jul (-0.848, p＜0.001); P impacted biomass (Apr: 22.0 %, Jul: 18.8 %, Oct: 14.0 %) and Icariin-Flavonoids (Feb: 10.2 %). Soil K influenced plant K in Feb (-0.749), Apr (-0.561, p＜0.001); K was vital for biomass (Feb: 73.1 %, Oct: 42.7 %) and Icariin-Flavonoids (Jul: 21.8 %, Oct: 17.1 %). We Propose a strategy: moderate N in Feb and Jul; P supplementation in Apr and Jul; K adequacy in Feb and moderate in Jul-Oct. This strategy offers a theoretical basis for rational fertilization in E. pubescens cultivation, enhancing yield and quality, crucial for efficient utilization and sustainable development of medicinal plant resources.