Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N 2 O reductase-gene nosZ and N 2 O:N 2 partitioning from agricultural soils

• Published in: Scientific reports 2020-02, Vol.10 (1), p.2399
• Main Authors: Friedl, Johannes, Scheer, Clemens, Rowlings, David W, Deltedesco, Evi, Gorfer, Markus, De Rosa, Daniele, Grace, Peter R, Müller, Christoph, Keiblinger, Katharina M
• Format: Article
• Language: English
• ISSN: 2045-2322

Nitrification inhibitors (NIs) have been shown to reduce emissions of the greenhouse gas nitrous oxide (N O) from agricultural soils. However, their N O reduction efficacy varies widely across different agro-ecosystems, and underlying mechanisms remain poorly understood. To investigate effects of the NI 3,4-dimethylpyrazole-phosphate (DMPP) on N-turnover from a pasture and a horticultural soil, we combined the quantification of N and N O emissions with N tracing analysis and the quantification of the N O-reductase gene (nosZ) in a soil microcosm study. Nitrogen fertilization suppressed nosZ abundance in both soils, showing that high nitrate availability and the preferential reduction of nitrate over N O is responsible for large pulses of N O after the fertilization of agricultural soils. DMPP attenuated this effect only in the horticultural soil, reducing nitrification while increasing nosZ abundance. DMPP reduced N O emissions from the horticultural soil by >50% but did not affect overall N  + N O losses, demonstrating the shift in the N O:N ratio towards N as a key mechanism of N O mitigation by NIs. Under non-limiting NO availability, the efficacy of NIs to mitigate N O emissions therefore depends on their ability to reduce the suppression of the N O reductase by high NO concentrations in the soil, enabling complete denitrification to N .