Effects of planting spacing and potassium fertilizer rates on the growth, development and seed yield of Atractylodes macrocephala Koidz. in Sa Pa, Vietnam

Atractylodes macrocephala Koidz. is a valuable medicinal plant widely used in traditional East Asian medicine, particularly for digestive disorders, diarrhea, abdominal distension, edema, night sweats and threatened miscarriage. This study was conducted in Sa Pa, Lao Cai Province, Vietnam, to identify suitable planting spacing and potassium fertilizer rates for the growth, development and seed yield of A. macrocephala. The experiment comprised four potassium treatments (0, 110, 135, and 160 kg K2O ha⁻1) and three planting spacings (30 × 20 cm, 30 × 30 cm, and 30 × 40 cm). The results indicated that planting spacing and potassium application affected plant height, canopy diameter, the number of primary branches and seed-yield components. The most suitable treatment for seed production comprised 15 t ha⁻1 farmyard manure, 5 t ha⁻1 wood ash, 86 kg P2O5 ha⁻1, 186 kg N ha⁻1 and 160 kg K2O ha⁻1, combined with a planting spacing of 30 × 30 cm. The harvested seed yield under this treatment was 210.52 kg ha⁻1.