Objectives The lack of systematic fertilization research has led to low seed yield and unstable quality in the seed production of Angelica dahurica var. formosana. Therefore, we investigated the effects of different nitrogen (N), phosphorus (P₂O₅), and potassium fertilizer (K₂O) amounts and ratios on seed yield and quality, aiming to establish a suitable fertilization technology for efficient and high-quality seed production.

Methods Field experiments were conducted in 2021 and 2022 in Chengdu, Sichuan Province, using the variety “Chuanzhi 2” A. dahurica var. formosana as the experimental material. A “3414” incomplete orthogonal regression design was employed, with four fertilization levels of nitrogen, phosphorus, and potassium, resulting in a total of 14 treatments. During the harvest period, we measured the seed yield, 1000-grain-weight, seed morphologyical and germination indices.

Results There was a significant interactive effect among the nitrogen, phosphorus, and potassium fertilizers on the seed yield of A. dahurica var. formosana. Treatment N₂P₂K₂ (N180.6 kg/hm², P₂O₅ 306.5 kg/hm², and K₂O 149.8 kg/hm²) was recorded the highest seed yield, 1000-grain-weight, seed length, seed width, vitality, germination rate, germination potential, and germination index, and the increment relative to no fertilization treatment N₀P₀K₀ were 83.3%, 27.3%, 16.4%, 18.9%, 23.3 percent points, 16.7 percent points, 24.0 percent points, and 28.2%, respectively. The grey correlation analysis result showed that the effect of seed yield ranked the highest on seed vitality, followed by germination rate, germination potential, and 1000-grain-weight. The highest weighted correlation coefficient (0.825) and the equal weight correlation coefficient (0.824) were thereby appeared in N₂P₂K₂ treatment, and the second high values (0.745 and 0.751) were in treatment N₁P₂K₁ (N 90.3 kg/hm², P₂O₅ 306.5 kg/hm², and K₂O 74.9 kg/hm²). Within the fertilization ranges, the seed yield increased first and then decreased with the increase of any N, P₂O₅, or K₂O levels, and reached maximum in N₂P₂K₂ treatment. According to the fitted ternary quadratic fertilizer effect equation, the highest seed yield of A. dahurica var. formosana (1766.6 kg/hm²) was obtained with nitrogen fertilizer (N), phosphorus fertilizer (P₂O₅), and potassium fertilizer (K₂O) of 177.0, 274.6, and 133.7 kg/hm², respectively.

Conclusions Appropriate combination of nitrogen, phosphorus, and potassium fertilizers can significantly improve the yield and quality of A. dahurica var. formosana seeds. The recommended fertilization rates are N 177.0, P₂O₅ 274.6 and K₂O 133.7 kg/hm², and the suitable N: P₂O₅ : K₂O ratio is 1∶1.55∶0.75.