The excessive application of nitrogen (N) fertilizer causes N loss from agricultural soil, through leaching and gaseous losses, such as nitrous oxide (N₂O), which have a negative effect on the environment. Despite the critical importance of nitrification and denitrification in the nitrogen cycle, our understanding of the effect of the different ammonia oxidizers and denitrifying microbes in intensive vegetable cultivation soils on N₂O emissions is still limited.

The nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP), has been used to improve fertilizer use efficiency and reduce nitrogen losses from agricultural systems by slowing nitrification. However, its effects on nitrifier and denitrifier activities in intensive vegetable cultivation soils remain largely unknown. 

Dr LI Jie, a researcher of Institute of Applied Ecology, Chinese Academy of Sciences, conducted a research to assess the impacts of DMPP on N₂O emissions, ammonia oxidizers and denitrifying microbes in two different durations of intensive vegetable cultivation soils (cultivated 1 year and 29 years).

This study is valuable to evaluate how management will affect nutrient loss and greenhouse gas emissions in agricultural land and could be helpful to minimize the N₂O fluxes from agriculture ecosystems in practice. 

They found that DMPP addition could stimulate some changes in ammonia-oxidising bacteria (AOB) and nirK abundance in the two different cultivation vegetable soils, but had no effect on ammonia-oxidising archaea (AOA) and nirS, indicating that AOB and nirK might play a more important role in intensive cultivation vegetable soils.

The application of DMPP was more effective in reducing soil NO₃^--N content and N₂O emission, and delaying ammonia oxidation in the long-term cultivation soil than in the short-term cultivation soil.  

This study indicates that long-term cultivation soils with high N levels could induce significant shifts in nitrifying communities, and DMPP addition can be effective in mitigating N₂O emissions favouring more efficient N transformation in the long-term cultivation soil. 

The study entitled "Effects of 3,4-dimethylpyrazole phosphate (DMPP) on the abundance of ammonia oxidizers and denitrifiers in two different intensive vegetable cultivation soils" has been accepted in Journal of Soils and Sediments.  

This research is financially supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China.