Precision nutrient management in hydroponic blueberry (Vaccinium corymbosum L.) under climatic stress: uptake dynamics and accumulation patterns

The growing global demand for blueberries (Vaccinium corymbosum L.), driven by their nutraceutical benefits, requires optimizing both yield and fruit quality—an increasingly complex goal under the influence of abiotic stress and intensifying climatic extremes. Non-linear nutrient accumulation curves and net daily absorption rates were developed for macro and microelements from biomass and tissue concentration data over 200 days after transplanting (DAT). Second-order polynomial models (R²ₐdⱼ ≥ 0.94) revealed dynamic uptake patterns, identifying critical windows of high demand and net physiological remobilization. The first phase (60-90 DAT) exhibited maximum uptake of phosphorus (P), calcium (Ca), magnesium (Mg), sulfur (S), and immobile micronutrients such as iron (Fe) (0.13 mg plant⁻¹ day⁻¹), zinc (Zn), and manganese (Mn), essential for vegetative expansion. In contrast, nitrogen (N) showed a distinctive decline in net absorption (–51.45 mg plant⁻¹ day⁻¹) between 90-120 DAT, indicating significant internal remobilization towards reproductive organs. The final stage (150-200 DAT) was dominated by intensive potassium (K) uptake (54.76 mg plant⁻¹ day⁻¹) for fruit filling, while Ca and micronutrient absorption (particularly boron [B] and copper [Cu]) plateaued or declined, reflecting limited xylem transport under the high temperatures (>39 °C) and vapor pressure deficits recorded at the site. These absorption dynamics were strongly influenced by root-zone thermal stress, which reached a peak of 39 °C during the late stages, affecting the nutrient use efficiency and final fruit quality. These results provide a quantitative foundation for designing fertilization strategies aligned with phenological development and aimed at enhancing nutrient use efficiency and fruit quality under tropical conditions.