Chitosan coated Zn/P nanofertilizer regulate phytotoxicity and nutrient delivery via nanoscale-specific translocation pathway

Excessive agrochemical inputs have degraded agro-ecosystems, prompting the search for delivery systems that supply nutrients with minimal losses. To synthesize a single carrier that simultaneously provides P and Zn, and to quantify its seed-germination and hydroponic toxicity thresholds, nutrient-release kinetics, and uptake efficiency versus conventional fertilizers. Zn-doped nano-hydroxyapatite was surface-coated with chitosan (Zn-nHAP@CS; hydrodynamic diameters of 351.3 ± 10.9 nm, zeta potential ≈ +14.4 mV, 4.97 wt% Zn, 17.1 wt% P). Seed germination and hydroponic experiments indicated Zn-nHAP@CS at 200 mg/L is non-toxic, enhances root elongation, and promote nutrients accumulation. Particle-state nanofertilizer was physically separated from the released nutrients by a dialysis membrane. Zn-nHAP@CS in Directly exposure mode exhibited different ionome influence compared with In-Direct exposure mode and Zn ion. Compared to traditional fertilizers, Zn-nHAP@CS promotes the absorption of plant-essential nutrients by stimulating the uptake pathway of nanomaterials through direct contact with the plant rhizosphere. Furthermore, the sustained-release effect of the chitosan coating enables the long-term controlled release of Zn and P nutrients in the rhizosphere, thereby reducing the wasteful leaching of agricultural chemicals and environmental pollution caused by rainfall. These findings highlight the potential of Zn-doped and chitosan coating nano-hydroxyapatite as an effective nanofertilizer, contributing to more environmentally friendly, sustainable agricultural practices. • A novel nanofertilizer for simulating release P and Zn was proposed. • Nanofertilizer promoted root elongation and reduced the oxidative damage than Zn 2+ . • Dialysis membrane device was designed to compare the nanoparticles and ion toxicity. • The nutrients homeostasis variation proved the distinct nanoscale influence on plant. • The direct contact of nanofertilizer induced more positive influence on plant growth.