Influence of Chitosan on the Degradation Rate and Efficiency of DMPP

ABSTRACT Background and Aim Although 3,4‐dimethylpyrazole phosphate (DMPP) has been recognized as one of the most effective nitrification inhibitors (NIs), its application is not without drawbacks. Methods To further optimize the formulation of DMPP‐based fertilizers, we combined DMPP with chitosan under controlled conditions and investigated their combined impacts on soil N conversion characteristics, the activity of N‐related enzymes, rates of ammonia (NH 3 ) volatilization, and nitrous oxide (N 2 O) emission. Results The results demonstrate that chitosan alone regulates N conversion processes, including inhibiting urease activity (UA) to delay urea hydrolysis and reducing potential nitrification rate (PNR) and nitrate reductase activity (NRA) to inhibit both nitrification and denitrification processes. It also promotes microbial assimilation of fertilizer‐derived N, while reducing the accumulation of NH 3 volatilization and N 2 O emissions compared to urea alone. Chitosan did not significantly affect the degradation rate of DMPP ( p > 0.05); however, its presence reduced the effectiveness of DMPP. Compared to DMPP alone, chitosan promoted nitrification and denitrification intensities after 63 days of incubation. Structural equation models (SEM) revealed that the synergistic interaction between chitosan and DMPP influenced PNR, which was identified as a key factor driving NH 3 volatilization losses. Furthermore, the presence of chitosan intensified nitrification and denitrification (as determined by enzyme activity), leading to increased accumulated N 2 O emissions. Although the combination does not produce entirely positive effects, the reduction in NH 3 volatilization losses far exceeds the increase in N 2 O emissions losses. Conclusion On balance, we conclude that the combination provides more favorable environmental benefits, whereas its effectiveness still needs to be further validated in agricultural practices.