Abstract <p>Fulvic acid-rich biostimulants have gained attention for their ability to enhance plant growth, nutrient uptake, and stress tolerance in sustainable agricultural systems. This study investigated the effects of different application rates and timing strategies of a fulvic acid-rich biostimulant on cauliflower (<i>Brassica oleracea</i> var. botrytis) growth, physiology, nutrient accumulation, and yield. A factorial experiment was conducted, assessing key parameters such as growth parameters, chlorophyll content, fluorescence traits, gas exchange parameters, plant macronutrient content. Multivariate analysis revealed that the application strategy significantly influenced plant responses, with PC1 and PC2 explaining 55.78 and 17.86% of the variance, respectively. Structural Equation Modeling (SEM) confirmed that the biostimulant had a direct impact on plant nutrition (β = 0.93), which further influenced growth (β = 0.20) and physiology (β = 0.38), ultimately affecting yield (β = 0.46). The results indicated that a 20 L/ha fulvic acid application at 100% during early growth (T100) led to the highest leaf P content, whereas split applications (T20/20/60) at 40 L/ha significantly increased inflorescence K content. Correlation analysis highlighted key trade-offs, with leaf P content and chlorophyll <i>a</i> negatively associated with dry biomass, suggesting nutrient allocation trade-offs between physiological efficiency and biomass accumulation. These findings provide insights into optimizing fulvic acid-rich biostimulant applications for maximizing nutrient uptake and productivity in short-cycle crops. While the observed responses were most pronounced in plastic traits such as chlorophyll <i>a</i> content and F₀, the potential long-term effects on perennial crops warrant further investigation. The study underscores the importance of tailoring biostimulant application strategies to enhance nutrient use efficiency and sustainable production in tropical agriculture.</p>