Effects of different application rates of 3,5-dimethylpyrazole on soil ammonium nitrification and crop growth

3,5-dimethylpyrazole(DMP) was proved to have a significant nitrification-inhibitory effect.The aim of this study is to investigate the effects of different application rates of DMP on yield,nitrogen use efficiency and crude protein content of spring wheat and rice by means of laboratory incubation combining with pot experiments.The results showed that applying DMP equivalent to 0.6%1.0% of urea-N(0.80.9 g/g,dry soil) could inhibit soil nitrification significantly,and its inhibitory effect increased with increasing DMP rate.Compared with single application of urea,applying 1.0%DMP increased soil NH4+-N content by more than 30%,but reduced soil NO3--N content by about 20%.Applying DMP equivalent to 0.8%1.0% of ureaN had no significant effects on spring wheat,but it could significantly increase rice yield,and nitrogen apparent use efficiency of both two crops.Compared with dicyandiamide(DCD),applying DMP with same application rate increased crude protein content and nitrogen apparent use efficiency of rice,while no significant difference in yield was observed for those two treatments.Therefore,DMP would be another promising new nitrification inhibitor.