Influence of Seaweed Extracts on the Degradation and Effectiveness of 3,4-Dimethylpyrazole Phosphate

3,4-Dimethylpyrazole phosphate (DMPP) is acknowledged as one of the most efficient nitrification inhibitors (NIs); however, researchers have suggested that its effectiveness needs to be further improved. The authors combined the biostimulant seaweed extract (SE) with DMPP and conducted an indoor incubation experiment to initially investigate the impact of the influence of SE on the degradation and effectiveness of DMPP. Meanwhile, a method for the extraction and determination of DMPP was developed. DMPP performed better, with a longer effective time in loess than black soil, and SE showed a delayed effect on DMPP degradation of DMPP at the beginning of the incubation and then accelerated the degradation process. This was attributed to the adsorption effect of SE on DMPP, consequently reducing its effectiveness. The SE delayed the hydrolysis of urea in various soils; however, no significant impact on urease activity was observed (P < 0.05) (P < 0.05). Furthermore, it also increased potential nitrification rate (PNR) from 10 to 21 days and promoting the rapid transformation of NH4+-N in black soil. The SE reduced PNR within 21 days and inhibited nitrification in loess. In addition, the SE appeared to mitigate the adverse effects of excessive nitrogen on microorganisms The combination of DMPP and SE was not conducive to the inhibition of soil nitrification, and this formulation in field applications requires further investigation.