Abstract
<title>Abstract</title> <p> Purpose This study evaluated the interactive effects of nitrogen (N) and magnesium (Mg) fertilization on growth, yield, spear quality, nitrate accumulation, and root system architecture of greenhouse-grown asparagus ( <italic>Asparagus officinalis</italic> L.) under Northern Vietnam conditions. Methods A factorial experiment was conducted using three nitrogen rates (3, 4.5, and 6 g N pot⁻¹) and three magnesium rates (0, 1, and 2 g MgO pot⁻¹) arranged in a completely randomized design with three replications. Plant growth, chlorophyll content, spear yield, quality traits, root morphology, and root anatomy were evaluated. Pearson correlation and principal component analysis (PCA) were performed to identify relationships among productivity-related traits. Results Moderate nitrogen supply (4.5 g pot⁻¹) combined with 1 g MgO pot⁻¹ significantly improved yield, spear quality, chlorophyll content, and root development. Excessive nitrogen (6 g pot⁻¹) increased nitrate accumulation without proportional yield improvement and reduced root growth. Correlation and PCA results showed that productivity during the first harvest was primarily associated with aboveground traits, whereas root system architecture became increasingly important during the second harvest. Root length, diameter, and volume were strongly associated with harvested yield. Conclusions These findings demonstrate that balanced N–Mg nutrition promotes asparagus productivity by coordinating root structural development with physiological performance rather than simply increasing nutrient supply. The transition from shoot-dependent to root-mediated productivity provides new insight into nutrient-response mechanisms in perennial asparagus and highlights root system development as a key target for improving nutrient-use efficiency and sustainable greenhouse production. </p>