Dissimilatory nitrate reduction to ammonium (DNRA), not denitrification dominates nitrate reduction in subtropical pasture soils upon rewetting

Friedl, Johannes; Rosa, Daniele De; Rowlings, David; Grace, Peter R.; Müller, Christoph; Scheer, Clemens

doi:10.1016/j.soilbio.2018.07.024

Cited by 120 publications

(52 citation statements)

References 66 publications

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“…The main source of N 2 O in both soils was denitrification, accounting for more than 90% of N 2 O produced ( Fig. 2), which is in line with previous results from both field 11 and laboratory studies 10,12 . The ability of soils to act as an N 2 O sink, i.e.…”

Section: Discussionsupporting

confidence: 91%

“…This increase has however important implications for N-turnover, in particular for the sandy CL as soil with limited labile C availability. DMPP increased DNRA by a factor >5 in the sandy CL, suggesting labile C promoted NO 3 − consumption via DNRA 10,23 . DNRA competes with denitrification for available NO 3 − , but the magnitude of DNRA in the sandy CL was insignificant regarding NO 3 − availability for denitrification.…”

Section: Discussionmentioning

confidence: 91%

“…Specific background samples were taken above the respective soil microcosms treated with NH 4 15 NO 3 at 60 atom % (c) for 15 N 2 analysis before closing the tubes. The entire headspace atmosphere was sampled 24 and 48 h after closure using a gas-tight syringe from soil microcosms a, b and c. After the 24 h gas sampling, the Suba-seals were removed for 10 minutes, allowing the headspace atmosphere to equilibrate 10 . Gas samples were transferred into pre-evacuated 12 ml exetainer tubes with a double wadded Teflon/silicon septa cap (Labco Ltd, Buckinghamshire, UK) and stored until N 2 O and CO 2 analysis by gas chromatography (Shimadzu GC-2014).…”

Section: Methodsmentioning

confidence: 99%

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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: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

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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

Self Cite

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“…In subterranean estuaries with high NO 3 − concentrations, higher rates of denitrification are often facilitated by higher dissolved organic carbon, introduced into subterranean estuaries by tidal and wave actions (Janssen et al 2005;Kroeger and Charette 2008). In systems where NO 3 − is limiting, high dissolved organic carbon together with iron (Fe 2+ ) and sulphide (S 2− ) are shown to favor the predominance of dissimilatory NO 3 − reduction to ammonium over denitrification; however, reports of the occurrence of dissimilatory NO 3 − reduction to ammonium in sandy subterranean estuaries are scarce and mostly reported in estuaries (Kessler et al 2018) and in soils (Friedl et al 2018). To date, the importance of anammox in coastal subterranean estuaries remained ambiguous.…”

mentioning

confidence: 99%

Biogeochemical attenuation of nitrate in a sandy subterranean estuary: Insights from two stable isotope approaches

Wong

Applegate

Poh

et al. 2020

Limnology & Oceanography

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The role of permeable sediments and subterranean estuaries as coastal nutrient filters is a question of key interest, particularly in areas with high nitrogen loadings. Here, we evaluated the effectiveness of a sandy subterranean estuary in cycling and removing nitrate using stable isotopes of N and O at natural (δ15N‐NO3− and δ18O‐NO3−) and enriched levels (15N). Isotopes were used in conjunction with flow through reactors under anoxic conditions to quantify (1) the overall enrichment factor (15ε) of nitrate removal processes which was then applied to estimate the in situ percentage of nitrate removal within the subterranean estuary and (2) the potential rates of denitrification, dissimilatory nitrate reduction to ammonium, and anammox. We found that 15ε varied between −24 and −34‰ and were positively correlated with nitrate concentrations and the percentage of organic carbon added to the sediments. Using these 15ε values in a Rayleigh distillation model resulted in an estimated average of 34% ± 14% nitrate removal within the subterranean estuary, less than half of the percentage estimated using the nitrate‐salinity mixing model (66% ± 28%). Denitrification was the most dominant nitrate removal pathway within the subterranean estuary with potential rates among the highest denitrification rates reported for both permeable and cohesive sediments. The contribution of dissimilatory nitrate reduction to ammonium showed significant seasonal variation while the rates of anammox were consistent throughout the study. We suggest that the spatial shift of the subterranean estuary is the most likely explanation for the seasonal differences in the rates of denitrification and dissimilatory nitrate reduction to ammonium.

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“…A limitation of this method is that it does not provide explicit tracking of the fate of nitrate disappearance and thus cannot discriminate between pathways of denitrification or dissimilatory nitrate reduction to ammonium (DNRA). In situations where DNRA is of concern, namely C-rich soils (SOC > 4%) at low redox potentials (Friedl et al 2018), nitrate disappearance would be the result of the combined processes of denitrification and DNRA. Ammonium accumulation would be the result of net N mineralization and DNRA.…”

Section: Methodsmentioning

confidence: 99%

Simultaneous measurement of net nitrogen mineralization and denitrification rates in soil using nitrification inhibitor 3,5-dimethylpyrazole

et al. 2020

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A practical means to quantify the response of the rates of net N mineralization and denitrification over a wide range of soil water contents is generally lacking. This study examined the potential to use a nitrification inhibitor (NI) assay system to simultaneously estimate the rates of net N mineralization and denitrification, and applied the NI assay to assess the effect of water content on net N mineralization and denitrification rates in two soils with contrasting soil texture. The compound 3,5-dimethylpyrazole (DMP) applied at a rate of 200 mg kg−1 was found to provide essentially complete inhibition of nitrification over the duration of the soil incubation for two soils with contrasting soil texture (clay loam vs. sandy loam) and over a range of soil water contents (35%, 55%, and 85% water-filled pore space). This allowed net N mineralization to be estimated as the accumulation of soil ammonium ([Formula: see text]) and of denitrification as the disappearance of added nitrate ([Formula: see text]). Addition of DMP resulted in a small increase in soil respiration rate but did not appear to influence the rate of net soil N mineralization. The NI assay provides a practical means to quantify the rates of net N mineralization and denitrification simultaneously over a wide range of soil water contents. The assay can be readily scaled up to routinely test multiple soils in an efficient manner, has limited material costs, and is also relatively simple to perform.

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Dissimilatory nitrate reduction to ammonium (DNRA), not denitrification dominates nitrate reduction in subtropical pasture soils upon rewetting

Cited by 120 publications

References 66 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

Biogeochemical attenuation of nitrate in a sandy subterranean estuary: Insights from two stable isotope approaches

Simultaneous measurement of net nitrogen mineralization and denitrification rates in soil using nitrification inhibitor 3,5-dimethylpyrazole

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