Influence of Planting Density and NPK Fertilizer Rates on Growth, Yield, and Bacoside Content of Bacopa monnieri under Field Conditions in Vietnam

HistoryBacopa monnieri is an important medicinal herb valued for its bacoside-rich biomass and broad pharmaceutical applications.This study evaluated the combined effects of planting density and NPK fertilizer rates on growth performance, biomass yield, and bacoside accumulation under field conditions in Thanh Hoa Province, Vietnam during two consecutive cropping seasons (2024-2025).A two-factor randomized complete block design with three replications was implemented, comprising three planting densities (15 × 10, 15 × 15, and 15 × 20 cm) and four N-P2O5-K2O application rates (125-50-50, 150-60-60, 175-70-70, and 200-80-80 kg ha -1 ).Data were analyzed using two-way ANOVA, and treatment means were compared using the LSD test at P≤0.05.Both factors and their interaction significantly influenced phenological development, leaf morphology, stem diameter, biomass production, and bacoside concentration.The highest dry biomass yield (124.52 t ha -1 ) and elevated bacoside content (3.39-3.50%)were obtained under the combination of 15 × 15 cm spacing and 175-70-70 to 200-80-80 kg ha -1 fertilizer rates, whereas the lowest values (101.52 t ha -1 and 2.39%) were recorded under dense planting with low fertilizer input.An intermediate planting density combined with moderate to high fertilizer rates resulted in vigorous vegetative growth and superior yield performance.Importantly, bacoside concentration was maintained or enhanced under these treatments, indicating no reduction in phytochemical quality under improved agronomic conditions.These findings demonstrate that the significant interaction between planting density and nutrient supply should be optimized concurrently to maximize both productivity and medicinal value of B. monnieri under Vietnamese agro-ecological conditions.