The 15N-Gas flux method for quantifying denitrification in soil: Current progress and future directions

Micucci, Gianni; Sgouridis, Fotis; McNamara, Niall; Krause, Stefan; Lynch, Iseult; Roos, Felicity; Well, Reinhard; Ullah, Sami

doi:10.1016/j.soilbio.2023.109108

Cited by 7 publications

(8 citation statements)

References 117 publications

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“…One way to increase the sensitivity of the 15 NGF is to combine it with the use of an artificial atmosphere depleted in N 2 . As shown in Micucci et al (2023;Fig. 7), reducing the atmospheric N 2 concentration below 10 % highly increases the sensitivity of the 15 NGF.…”

Section: Introductionmentioning

confidence: 91%

“…Then, we calculated a p the 15 N enrichment of the soil nitrate pool undergoing denitrification and the coefficient d' (where a prime is used for N 2 O emissions and distinguish them from N 2 emissions, see Micucci et al, 2023) which represents the proportion of total N 2 O that derives from denitrification, with the method of Mulvaney and Boast (1986). These quantities can also be determined with the method of Arah (1992) and both methods have been used and compared during Experiment 1.…”

Section: N 2 O Isotopic Calculationsmentioning

confidence: 99%

“…This model is based on a revised version of the model of Hutchinson and Mosier (1981). It should be noted that emissions of 15 N-labelled molecules induce further diffusive issues that cannot be totally corrected through this model (Well et al, 2019b;Micucci et al, 2023). Fluxes from the chambers were measured on a per surface basis.…”

Section: Static Chamber Flux Calculationsmentioning

confidence: 99%

“…Finally, the 15 NGF uses 15 N-labelled nitrate tracer applied to soil incubated in gas tight vessels under laboratory conditions or within static chambers in field applications to measure the abundance of 15 N atoms in both denitrified N 2 and N 2 O molecules (Stevens and Laughlin 2002;Ruser et al, 2006;Baily et al, 2012;Sgouridis and Ullah, 2015;Deppe et al, 2017;Rummel et al, 2021;Liu et al, 2022a). The 15 NGF can be used with two main models of calculation, the "Mulvaney & Boast" model (based on Mulvaney and Boast, 1986) or the "Arah" model (based on Arah, 1992), as recently reviewed in Micucci et al (2023). They both use the distribution of the 15 N atoms in the N 2 and N 2 O isotopologues (molecules with same atomic identity but different isotopic composition) to derive the fluxes of denitrification, but they differ in their approach.…”

Section: Introductionmentioning

confidence: 99%

“…More detail can be found in Micucci et al (2023) and in this study but briefly, by discarding the measurement of the 30 N 2 molecules (for which the IRMS sensitivity is very limited) and by focusing on the 29 N 2 molecules only; while the 15 N enrichment of the soil denitrifying pool is determined with the N 2 O data, a better sensitivity can be achieved (Stevens and Laughlin, 2001;Spott et al, 2006;Sánchez-García et al, 2014;Friedl et al, 2020). This approach assumes that both gases originate from the same and sole denitrifying pool (Bergsma et al, 2001) and that no hybrid molecules are emitted (Phillips et al, 2016;Micucci et al, 2023). Using this method enabled Baily et al (2012) to report a sensitivity 16 times greater than when using 29 N 2 and 30 N 2 data.…”

Section: Introductionmentioning

confidence: 99%

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Towards enhanced sensitivity of the 15N Gas Flux method for quantifying denitrification in soil

Micucci

Sgouridis

Krause

et al. 2022

Preprint

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Denitrification is one of the major pathways of nitrogen (N) output from soil. In this process, soil nitrate (NO3-) is chemically reduced into dinitrogen (N2) through microbial respiration. Incomplete denitrification leads to the emission of nitrous oxide (N2O), a greenhouse gas 300 times more potent in inducing global warming than carbon dioxide (CO2). Denitrification is highly variable in space and time, which makes it one of the most unconstrained processes in the global N cycle. Measuring denitrification is challenging because it emits small amounts of N2, hardly distinguishable from the high N2 atmospheric background (78% in volume). The aim of this study was to increase the sensitivity of the 15N Gas Flux method (15NGF), which is considered today, the only suitable method for in situ measurement of denitrification. The 15NGF consists of injecting a stable isotopic tracer (15NO3-) in a pre-determined area of soil and quantifying N2 production via its isotopic composition over time under an enclosed chamber. In order to increase the sensitivity of this method, we aimed to optimize two parameters: the quantity of tracer injected and the N2 background concentration. Increasing the amount of available nitrate represents a risk of stimulating microbes. Reducing the atmospheric N2 background in situ can be challenging because of leaks and diffusion issues. Our study focused on three different types of agricultural land uses: Arable, Herbal-Rich ley and Grass Clover ley. All three land uses were part of the same experimental field and the leys were in a 3-year rotation with the Arable. We first incubated homogenised soil under lab conditions and under different treatments of added tracer in order to increase sensitivity and observe if a microbial stimulation occurred. Gravimetric moisture was raised to 45% (on a dry mass basis) to simulate a rainfall event and increase the magnitude of denitrification. First experiments showed no detectable amount of evolved N2 and thus, a custom-made gas mix had to be used. This gas mix contained 20% of dioxygen (O2), 5% of N2 and 75% of Helium (He) and was used to replace the native atmosphere in the incubation chambers.First results showed no significant difference in denitrified N for the ley soils treated with different amounts of tracer. The Arable soil however seemed to have been stimulated when using greater quantities of tracer but further results are expected to confirm this. The Arable treatment also had the highest potential of denitrification in the lab with a mean value of 6.26 x 10-1 &#181;gN/kg/h of emitted N2, compared to the leys who both emitted 1.65 x 10-1 &#181;gN/kg/h. The theoretical sensitivity is increased 24 times for the detection 29N2 and 97 times for the detection of 30N2 when using the gas mix and a 50% tracer enrichment, compared to a 20% enrichment under atmospheric conditions.Finally, we measured denitrification directly in-situ using higher quantities of tracer and the custom-made gas mix. This was done using either modified greenhouse gas chambers or sealed plastic liners.

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Section: Introductionmentioning

confidence: 91%

Section: N 2 O Isotopic Calculationsmentioning

confidence: 99%

Section: Static Chamber Flux Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Towards enhanced sensitivity of the 15N Gas Flux method for quantifying denitrification in soil

Micucci

Sgouridis

Krause

et al. 2022

Preprint

View full text Add to dashboard Cite

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Lysimeter-based full fertilizer 15N balances corroborate direct dinitrogen emission measurements using the 15N gas flow method

Yankelzon,

Schilling,

Butterbach-Bahl

et al. 2024

Biol Fertil Soils

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The 15N gas flux (15NGF) method allows for direct in situ quantification of dinitrogen (N2) emissions from soils, but a successful cross-comparison with another method is missing. The objectives of this study were to quantify N2 emissions of a wheat rotation using the 15NGF method, to compare these N2 emissions with those obtained from a lysimeter-based 15N fertilizer mass balance approach, and to contextualize N2 emissions with 15N enrichment of N2 in soil air. For four sampling periods, fertilizer-derived N2 losses (15NGF method) were similar to unaccounted fertilizer N fates as obtained from the 15N mass balance approach. Total N2 emissions (15NGF method) amounted to 21 ± 3 kg N ha− 1, with 13 ± 2 kg N ha− 1 (7.5% of applied fertilizer N) originating from fertilizer. In comparison, the 15N mass balance approach overall indicated fertilizer-derived N2 emissions of 11%, equivalent to 18 ± 13 kg N ha− 1. Nitrous oxide (N2O) emissions were small (0.15 ± 0.01 kg N ha− 1 or 0.1% of fertilizer N), resulting in a large mean N2:(N2O + N2) ratio of 0.94 ± 0.06. Due to the applied drip fertigation, ammonia emissions accounted for < 1% of fertilizer-N, while N leaching was negligible. The temporal variability of N2 emissions was well explained by the δ15N2 in soil air down to 50 cm depth. We conclude the 15NGF method provides realistic estimates of field N2 emissions and should be more widely used to better understand soil N2 losses. Moreover, combining soil air δ15N2 measurements with diffusion modeling might be an alternative approach for constraining soil N2 emissions.

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Determining N2O and N2 fluxes in relation to winter wheat and sugar beet growth and development using the improved 15N gas flux method on the field scale

Eckei,

Well,

Maier

et al. 2024

Biol Fertil Soils

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The objectives of this field trial were to collect reliable measurement data on N2 emissions and N2O/(N2O + N2) ratios in typical German crops in relation to crop development and to provide a dataset to test and improve biogeochemical models. N2O and N2 emissions in winter wheat (WW, Triticum aestivum L.) and sugar beet (SB, Beta vulgaris subsp. vulgaris) were measured using the improved 15N gas flux method with helium–oxygen flushing (80:20) to reduce the atmospheric N2 background to < 2%. To estimate total N2O and N2 production in soil, production-diffusion modelling was applied. Soil samples were taken in regular intervals and analyzed for mineral N (NO3− and NH4+) and water-extractable Corg content. In addition, we monitored soil moisture, crop development, plant N uptake, N transformation processes in soil, and N translocation to deeper soil layers. Our best estimates for cumulative N2O + N2 losses were 860.4 ± 220.9 mg N m−2 and 553.1 ± 96.3 mg N m−2 over the experimental period of 189 and 161 days with total N2O/(N2O + N2) ratios of 0.12 and 0.15 for WW and SB, respectively. Growing plants affected all controlling factors of denitrification, and dynamics clearly differed between crop species. Overall, N2O and N2 emissions were highest when plant N and water uptake were low, i.e., during early growth stages, ripening, and after harvest. We present the first dataset of a plot-scale field study employing the improved 15N gas flux method over a growing season showing that drivers for N2O and N2O + N2 fluxes differ between crop species and change throughout the growing season.

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The 15N-Gas flux method for quantifying denitrification in soil: Current progress and future directions

Cited by 7 publications

References 117 publications

Towards enhanced sensitivity of the 15N Gas Flux method for quantifying denitrification in soil

Towards enhanced sensitivity of the 15N Gas Flux method for quantifying denitrification in soil

Lysimeter-based full fertilizer 15N balances corroborate direct dinitrogen emission measurements using the 15N gas flow method

Determining N2O and N2 fluxes in relation to winter wheat and sugar beet growth and development using the improved 15N gas flux method on the field scale

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