More than half of the fertilizers used today are in the form of ammonia (NH3) or ammonium (NH4+). However, only a small proportion of nitrogen (N) is utilized by plants, and as much as 50-70% of N from fertilizers is lost through leaching in the form of NO3- or N2O emission as mediated by nitrification. Nitrapyrin, dicyandiamide (DCD) and ammonium thiosulfate (ATS) have been commercially used as nitrification inhibitors (NIs) in the United States to preserve N in the agricultural soil through reduced nitrification. However, there is a lack of understanding of the mechanisms of the inhibition processes. This research is to fill this knowledge gap by linking microbial activities to inhibition observations using mathematical modeling and molecular biology tools. In this research, the conversions of NH4+ to NO2- and NO3- and emission of N2O were monitored in the presence of nitrapyrin, DCD and ATS at different concentrations, and the inhibitory effects of NIs were quantified based on the mathematical modeling against the experimental data. Activities of ammonium oxidizer and nitrite oxidizer were recorded and were further verified by PCR analysis. At the same time, microbial-mediated NI degradation was also studied. The correlation of the inhibition effects, ammonium oxidizer and nitrite oxidizer activities, and NI degradation kinetics was discussed.

Mechanistic investigation of nitrification inhibition and subsequent nitrous oxide (N2O) emission

253rd National Meeting (2017)

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