An improved <sup>15</sup>N tracer approach to study denitrification and nitrogen turnover in soil incubations

Scheer, Clemens; Meier, R.; Brüggemann, Nicolas; Grace, Peter R.; Dannenmann, Michael

doi:10.1002/rcm.7689

Cited by 11 publications

(3 citation statements)

References 41 publications

(118 reference statements)

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“…In the loam, NO 3 − levels were above those measured at the respective field site, which is also reflected in higher N 2 O d /(N 2 O d + N 2 ) ratios 11 . This phenomenon often occurs in incubation studies, where the absence of plant uptake, pre-incubation 33,34 , and the addition of glucose 26 increases NO 3 − levels in the soil. It is therefore important to consider N substrate availability when interpreting the effects of NIs on rate and N 2 O:N 2 partitioning of denitrification losses.…”

Section: Discussionmentioning

confidence: 99%

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Friedl

Scheer

Rowlings

et al. 2020

Sci Rep

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Nitrification inhibitors (NIs) have been shown to reduce emissions of the greenhouse gas nitrous oxide (n 2 O) from agricultural soils. However, their N 2 O reduction efficacy varies widely across different agroecosystems, 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 2 and N 2 O emissions with 15 N tracing analysis and the quantification of the N 2 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 2 O is responsible for large pulses of N 2 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 2 O emissions from the horticultural soil by >50% but did not affect overall n 2 + N 2 O losses, demonstrating the shift in the N 2 o:n 2 ratio towards N 2 as a key mechanism of N 2 O mitigation by NIs. Under non-limiting NO 3 − availability, the efficacy of NIs to mitigate N 2 O emissions therefore depends on their ability to reduce the suppression of the N 2 O reductase by high NO 3 − concentrations in the soil, enabling complete denitrification to N 2 .Agricultural soils have become the main source of anthropogenic nitrous oxide (N 2 O), a powerful greenhouse gas and the single most important substance depleting stratospheric ozone 1 . Delaying the conversion of ammonium (NH 4 + ) to nitrate (NO 3 − ), nitrification inhibitors (NIs) have been suggested as a means to reduce N 2 O emissions from agricultural soils. NIs demonstrated their efficacy across different cropping soils 2 , but results vary widely, and in particular in pasture soils the use of NIs had no or little effect on N 2 O emissions 3-5 . Despite a growing body of research on NIs, mechanisms and factors determining their efficacy to reduce N 2 O emission remain poorly understood 6 . The challenges to understand these mechanisms derive from the fact that N 2 O is formed via several different pathways in the soil matrix 7 , tightly coupled to different processes of N supply and consumption 8 . Critically, N 2 O can be further reduced to N 2 via the microbial-mediated process of denitrification, and the sole quantification of N 2 O as affected by NIs provides therefore only a limited insight into mechanisms of N 2 O mitigation using NIs.Microbial metabolic pathways can contribute via a wealth of different processes to N 2 O production and consumption, i.e. the reduction to N 2 in soils. Apart from abiotic processes, N 2 O formation can be categorized into www.nature.com/scientificreports www.nature.com/scientificreports/ nitrification-mediated pathways, denitrification and biotic formation of hybrid N 2 O 9 . Denitrification is generally assumed to be the main process contributing to overall N 2 O production from agricultu...

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Section: Discussionmentioning

confidence: 99%

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Friedl

Scheer

Rowlings

et al. 2020

Sci Rep

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“…However, this did not change the enrichment of the active denitrifying pool, which indicates a spatial separation of denitrification and nitrification, occurring in different micro-sites within the soil matrix. It has been shown that direct measurement of 15 N-NO 3 − using extraction and diffusion does not reflect the enrichment of the active NO 3 − pool undergoing denitrification, and the use of these data in denitrification rate calculations has been shown to result in unrealistically high N 2 flux rates 20,41 .…”

Section: Discussionmentioning

confidence: 99%

“…Another promising approach could be to use this system with a reduced N 2 atmosphere in the chamber headspace. This method has recently been used in field and lab studies and shown that it can significantly reduce the detection limit for N 2 fluxes 41,42 . However, it requires a rather complex set-up involving flushing of the headspace and the sub-soil with an artificial gas mixture that needs to be coupled to the automated sampling system.…”

Section: Discussionmentioning

confidence: 99%

Mobile continuous-flow isotope-ratio mass spectrometer system for automated measurements of N2 and N2O fluxes in fertilized cropping systems

Warner

Scheer

Friedl

et al. 2019

Sci Rep

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The use of synthetic N fertilizers has grown exponentially over the last century, with severe environmental consequences. Most of the reactive N will ultimately be removed by denitrification, but estimates of denitrification are highly uncertain due to methodical constraints of existing methods. Here we present a novel, mobile isotope ratio mass spectrometer system (Field-IRMS) for in-situ quantification of N 2 and N 2 O fluxes from fertilized cropping systems. The system was tested in a sugarcane field continuously monitoring N 2 and N 2 O fluxes for 7 days following fertilization using a fully automated measuring cycle. The detection limit of the Field-IRMS proved to be highly sensitive for N 2 (54 g ha −1 day −1 ) and N 2 O (0.25 g ha −1 day −1 ) emissions. The main product of denitrification was N 2 with total denitrification losses of up to 1.3 kg N ha −1 day −1 . These losses demonstrate sugarcane systems in Australia are a hotspot for denitrification where high emissions of N 2 O and N 2 can be expected. The new Field-IRMS allows for the direct and highly sensitive detection of N 2 and N 2 O fluxes in real time at a high temporal resolution, which will help to improve our quantitative understanding of denitrification in fertilized cropping systems.

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Carbon limits non-linear response of nitrous oxide (N2O) to increasing N inputs in a highly-weathered tropical soil in Sri Lanka

Liyanage

Grace

Scheer

et al. 2020

Agriculture, Ecosystems & Environment

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An improved ¹⁵N tracer approach to study denitrification and nitrogen turnover in soil incubations

Cited by 11 publications

References 41 publications

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Mobile continuous-flow isotope-ratio mass spectrometer system for automated measurements of N2 and N2O fluxes in fertilized cropping systems

Carbon limits non-linear response of nitrous oxide (N2O) to increasing N inputs in a highly-weathered tropical soil in Sri Lanka

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An improved 15N tracer approach to study denitrification and nitrogen turnover in soil incubations

Cited by 11 publications

References 41 publications

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N-turnover, the N2O reductase-gene nosZ and N2O:N2 partitioning from agricultural soils

Mobile continuous-flow isotope-ratio mass spectrometer system for automated measurements of N2 and N2O fluxes in fertilized cropping systems

Carbon limits non-linear response of nitrous oxide (N2O) to increasing N inputs in a highly-weathered tropical soil in Sri Lanka

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An improved ¹⁵N tracer approach to study denitrification and nitrogen turnover in soil incubations