Novel nitrification inhibitor produced by immobilizing 3,4-dimethylpyrazole using biogenic substances instead of chemicals have potential for sustainable agriculture

3,4-dimethylpyrazole (DMP)-based nitrification inhibitors (NIs) represent a valid chemical strategy to reduce nitrogen non-point source pollution. However, current immobilization techniques for DMP primarily focus on chemical substances, and research on the potential of biomacromolecules to improve the stability, environmental benefits, and agronomic effects of DMP-based NIs is still insufficient. Humic acid (HA) and DMP were used to synthesize a biologically macromolecule-immobilized NI (PBS) with enhanced stability and compared with 3,4-dimethylpyrazole phosphate (DMPP), a commercially available DMP-based NI immobilized with chemical substances. Differences in thermal stability, decomposition products, and pyrolysis kinetics were analyzed using thermogravimetric analysis coupled with Fourier transform infrared spectrometer and mass spectrometer (TG-IR-MS). The environmental and agronomic benefits were further evaluated at both soil and crop levels. Results showed that DMP-based NIs decomposes into small molecules such as aldehydes, ketones, nitrogen-containing compounds, and carbon dioxide upon heating. When immobilized with HA, DMP forms a supramolecular complex, increasing the degradation peak temperature of DMP by 45°C (to 217°C) due to high carbon residues. After being stored for two months with various nitrogen fertilizers, PBS exhibited only a 10 % degradation rate, making it suitable for fertilizer production and long-term storage. Additionally, PBS displayed superior nitrification inhibition performance and promoted root growth. Compared to DMPP, PBS encouraged denser, more branched secondary root growth and increased root thickness. These findings suggest that PBS, synthesized from DMP and HA is a promising, sustainable, and effective NI, emphasizing the potential of modifying DMP with natural biological macromolecules. •Synthesis of a novel nitrification inhibitor (PBS) with humic acid and 3,4-Dimethylpyrazole.•Volatilization of 3.4-dimethylpyrazole is reduced by immobilization with humic acid.•PBS reduces N2O emissions by 91.2 %. and promotes crop lateral root differentiation while increaseing root thickness.