From Nano-Signals to Bioavailability: Unlocking Active Phosphorus Loading by Nano-Biochar

Phosphorus (P) scarcity and fertilizer inefficiency pose critical challenges to global food security and aquatic ecosystem health. This study demonstrates that nanoscale structural heterogeneity plays a key role in controlling phosphorus bioavailability. We show that Canna indica, an abundant agricultural residue, can be transformed into high-performance nanobiochar (CNBC), which serves as a sustainable phosphorus carrier. Through an unprecedented analytical framework combining Fourier-transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS) with single-particle collision electrochemistry (SPCE), we directly probe real-time phosphate dynamics at individual nanoparticle surfaces for the first time. The analyses reveal surface-rich oxygenated functional groups and Ca(II)-bridged coordination networks that stabilize P in dual binding domains─strong complexes that act as long-term reservoirs and weakly bound species, enabling controlled desorption. Diffusive gradients in thin film (DGT) experiments link these nanoscale redox-binding features to soil-scale nutrient mobility, identifying an optimal particle-size range of 117–209 nm that maximizes bioavailable P while minimizing leaching losses. This cross-scale framework, from molecular interactions to macroscale nutrient diffusion, establishes mechanistic design principles for engineering nanoscale heterogeneity to align P release dynamics with plant uptake, advancing precision fertilization strategies that reduce environmental risk and close the nutrient–carbon cycle.