Precision nutrient management for mango in karst agroecosystems: An integrated leaf diagnostic and fertilization framework

• Integrated BLA and RF models established a precision diagnostic framework. • Optimal diagnostic thresholds were defined for 11 leaf nutrients. • Leaf P, Mn, and N were identified as primary yield-limiting factors. • Robust vegetative nutrient accumulation underpins high yield potential. • A karst-adapted quantitative fertilization regime was formulated. Mango ( Mangifera indica L.) is a key fruit crop in China's karst agroecosystems, yet its yield potential is constrained by the lack of site-specific nutrient management strategies. To address this gap, a precision nutrient management system was established for the cultivar 'Guire 82' by analyzing 523 samples from mature orchards. By integrating the boundary line approach (BLA) and random forest (RF) models, optimal leaf nutrient concentration thresholds were defined as follows: N (12.91–16.3 g/kg), P (0.93–1.23 g/kg), K (3.91–5.67 g/kg), Ca (15.56–23.26 g/kg), Mg (1.37–1.90 g/kg), S (1.28–1.93 g/kg), Fe (57.1–128.9 mg/kg), Mn (535–1265 mg/kg), Cu (6.33–10.47 mg/kg), Zn (12.07–19.5 mg/kg), and B (13.5–22.11 mg/kg). Simultaneously, the priority order for maintaining leaf nutrients within these optimal ranges was identified as: P > Mn > N > Zn > Fe > K > Mg > Ca > Cu > B > S. Nutrient partitioning analysis further revealed that sufficient nutrient accumulation in vegetative organs was a key characteristic associated with high yields (> 18 t/ha). Accordingly, theoretical annual per-tree nutrient requirements were quantified to sustain high productivity: 232 g N, 24.5 g P, 176 g K, 186 g Ca, 21.7 g Mg, 23.6 g S, 1340 mg Fe, 4680 mg Mn, 134 mg Cu, 332 mg Zn, and 299 mg B. Furthermore, path analysis indicated that soil fertility influences yield primarily by driving vegetative nutrient accumulation. Collectively, this study establishes a robust diagnostic and fertilization framework, providing precise quantitative guidance for optimizing mango nutrient management in karst agroecosystems.