scholarly journals Isotope and microbiome analysis indicates variety of N-cycle processes controlling N2O fluxes in a drained peatland forest soil

2021 ◽  
Author(s):  
Mohit Masta ◽  
Sharvari Gadegaonkar ◽  
Holar Sepp ◽  
Mikk Espenberg ◽  
Jaan Pärn Pärn ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Nitrogen Cycle ◽  
Site Preference ◽  
Ammonia Treatment ◽  
Nitrate Treatment ◽  
Lab Experiments ◽  
Nitrifier Denitrification ◽  
Multiple Processes ◽  
Oxygen Conditions ◽  
Production Mechanisms

<p>Nitrous oxide (N2O) is a major greenhouse gas whose presence in atmosphere is continuously increasing. Hence it’s important to understand its production and consumption mechanisms. During the summer of 2020, we conducted lab experiments using heavy nitrogen tracers of Potassium Nitrate 15N 98% atom (Sigma Aldrich) and Ammonium Chloride 15N 98% atom (Sigma Aldrich) under different moisture conditions to get an insight into N2O production mechanisms and on their dependence on soil moisture. We applied the tracer to peat samples (Kärevere, Estonia) placed in 36 (12 control, 12 nitrate treatment & 12 ammonia treatment) plastic buckets (radius-10cm, height-20cm) with soil height of 10 cm and a 10 cm head space left for gas collection. We installed oxygen sensors, water table indicators and temperature sensors on all buckets. We focused on studying physical conditions (soil oxygen, temperature, water table and soil moisture), gas (N2O) emission data, soil chemistry, gas isotope 15N, soil isotope and soil microbiology to get a complete picture of the processes involved in production of N2O gas. Under the ammonia treatment, emissions increased more than ten-fold which could be due to multiple processes of the nitrogen cycle in play. N2O emissions increased as the oxygen conditions shifted from anoxic (Omg/L=0) to sub-oxic (Omg/L=0.5–6) and then decreased as oxygen conditions reached the oxic (Omg/L>6) state. Furthermore, we witnessed negative site preference and 18O values during the nitrate treatment indicating nitrifier-denitrification. Under the ammonia treatment, we recorded both negative as well as high positive site preference values indicating presence of multiple production mechanisms. This was expected as ammonia triggers multiple processes in the nitrogen cycle. In some samples, we observed N2O consumption with little change in site preference as compared to the N2O producing samples. This indicates some bacterial-denitrification along with the prevailing nitrifier-denitrification. We also observed that under both treatments, heavy oxygen increased with increasing site preference. This indicates reduction of N2O (Ostrom et al, 2007) as redox supports 15N and 18O enrichments. After these lab experiments, we conducted the same experiment at a large scale in a drained peatland forest in Agali, Estonia. In this experiment, we established 1m2 triangle-shape mesocosms using experimental draining and flooding to achieve varying oxygen conditions. Preliminary results of qPCR analysis of N-cycle control genes support the domination of ammonia oxidation and denitrification as sources of N2O.</p>

Drip irrigation affects N2O emission differently depending on soil moisture status in an intensive vegetable production system

2021 ◽  
Author(s):  
Xiuchun Xu ◽  
Di Wu ◽  
Wei Zhang ◽  
Bang Ni ◽  
Xuan Yang ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Drip Irrigation ◽  
Production System ◽  
Nitrate Content ◽  
Site Preference ◽  
Vegetable Production ◽  
Flood Irrigation ◽  
Tomato Production ◽  
Production Region ◽  
Soil Moisture Status

<p>Plastic-shed vegetable production system is becoming the main type of vegetable production in China, while excessive irrigation and fertilization input lead to significant N loss by leaching, runoff, and gaseous N. The current study established a field experiment to investigate the effects of drip irrigation and optimized fertilization on vegetable yield, water and fertilizer efficiencies and N<sub>2</sub>O emission in a typical intensive plastic-shed tomato production region of China. The treatments include CK (no fertilization, flood irrigation), FFP (farmers’ conventional fertilization, flood irrigation), OPT1 (80% of FFP fertilization, flood irrigation), OPT2 (80% of FFP fertilization, drip irrigation). N<sub>2</sub>O isotopocule deltas, including δ<sup>15</sup>N<sup>bulk</sup>, δ<sup>18</sup>O and SP (the <sup>15</sup>N site preference in N<sub>2</sub>O), have been used to investigate microbial pathways of N<sub>2</sub>O production under different treatments. Our results showed: i) optimized fertilization and drip irrigation significantly improved the fertilizer and water use efficiency without reducing tomato yield, ii) compared with flood irrigation, drip irrigation decreased soil WFPS and soil ammonium content, but increased soil nitrate content. When soil moisture was higher than 60%WFPS, drip irrigation led to a decrease of N<sub>2</sub>O emission with lower N<sub>2</sub>O SP signature observed than that of food irrigation, suggesting a reduction of denitrification derived N<sub>2</sub>O. In contrast, drip irrigation significantly increased N<sub>2</sub>O emission and N<sub>2</sub>O SP value when soil moisture status was lower than 55% WFPS, which may be due to the enhanced nitrification or fungal denitrification derived N<sub>2</sub>O.</p>

scholarly journals A new look at an old concept: using <sup>15</sup>N<sub>2</sub>O isotopomers to understand the relationship between soil moisture and N<sub>2</sub>O production pathways

SOIL ◽  
2019 ◽  
Vol 5 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Katelyn A. Congreves ◽  
Trang Phan ◽  
Richard E. Farrell
Keyword(s):  
Soil Moisture ◽  
Mitigation Strategies ◽  
Soil Conditions ◽  
Site Preference ◽  
N2o Emissions ◽  
Spectroscopic Techniques ◽  
N2o Production ◽  
Nitrification And Denitrification ◽  
The Relationship ◽  
Source Partitioning

Abstract. Understanding the production pathways of potent greenhouse gases, such as nitrous oxide (N2O), is essential for accurate flux prediction and for developing effective adaptation and mitigation strategies in response to climate change. Yet there remain surprising gaps in our understanding and precise quantification of the underlying production pathways – such as the relationship between soil moisture and N2O production pathways. A powerful, but arguably underutilized, approach for quantifying the relative contribution of nitrification and denitrification to N2O production involves determining 15N2O isotopomers and 15N site preference (SP) via spectroscopic techniques. Using one such technique, we conducted a short-term incubation where N2O production and 15N2O isotopomers were measured 24 h after soil moisture treatments of 40 % to 105 % water-filled pore space (WFPS) were established for each of three soils that differed in nutrient levels, organic matter, and texture. Relatively low N2O fluxes and high SP values indicted nitrification during dry soil conditions, whereas at higher soil moisture, peak N2O emissions coincided with a sharp decline in SP, indicating denitrification. This pattern supports the classic N2O production curves from nitrification and denitrification as inferred by earlier research; however, our isotopomer data enabled the quantification of source partitioning for either pathway. At soil moisture levels < 53 % WFPS, the fraction of N2O attributed to nitrification (FN) predominated but thereafter decreased rapidly with increasing soil moisture (x), according to FN=3.19-0.041x, until a WFPS of 78 % was reached. Simultaneously, from WFPS of 53 % to 78 %, the fraction of N2O that was attributed to denitrification (FD) was modelled as FD=-2.19+0.041x; at moisture levels of > 78 %, denitrification completely dominated. Clearly, the soil moisture level during transition is a key regulator of N2O production pathways. The presented equations may be helpful for other researchers in estimating N2O source partitioning when soil moisture falls within the transition from nitrification to denitrification.

scholarly journals Revisiting the relationship between soil moisture and N<sub>2</sub>O production pathways by measuring <sup>15</sup>N<sub>2</sub>O isotopomers

2019 ◽  
Author(s):  
Kate A. Congreves ◽  
Trang Phan ◽  
Richard E. Farrell
Keyword(s):  
Soil Moisture ◽  
Pore Space ◽  
Mitigation Strategies ◽  
Soil Conditions ◽  
Site Preference ◽  
N2o Emissions ◽  
Spectroscopic Techniques ◽  
N2o Production ◽  
Nitrification And Denitrification ◽  
The Relationship

Abstract. Understanding the production pathways of potent greenhouse gases, such as nitrous oxide (N2O), is essential for accurate flux prediction and for developing effective adaptation and mitigation strategies in response to climate change. Yet, there remain surprising gaps in our understanding and precise quantification of the underlying production pathways – such as the relationship between soil moisture and N2O production pathways. A powerful, but arguably underutilized, approach for quantifying the relative contribution of nitrification and denitrification to N2O production involves determining 15N2O isotopomers and 15N site preference (SP) via spectroscopic techniques. Using one such technique we conducted a short-term incubation to precisely quantify the relationship between soil moisture and N2O production pathways. For each of three soils, microcosms were arranged in a complete random design with four replicates; each microcosm consisted of air-dried soil packed into plastic petri dishes wherein moisture treatments were established for water contents equivalent to 45 to 105 % water-filled pore space (WFPS). The microcosms were placed in 1-L jars and sealed; headspace samples were collected after 24-h and analyzed for total N2O concentrations using gas chromatography, and for 15N2O isotopomers using cavity ring-down spectroscopy. Relatively low N2O fluxes and high SP values indicted nitrification during dry soil conditions, whereas at higher soil moisture, peak N2O emissions coincided with a sharp decline in SP indicating denitrification. This pattern supports the classic N2O production curves from nitrification and denitrification as inferred by earlier research; however, our isotopomer data enabled the quantification of source partitioning for either pathway thereby providing clarity on N2O sources during the transition from nitrification to denitrification. At soil moisture levels  78 %, denitrification completely dominated. Clearly, the soil moisture levels during transition is a key regulation of N2O production pathways.

scholarly journals First on-line isotopic characterization of N<sub>2</sub>O above intensively managed grassland

2015 ◽  
Vol 12 (8) ◽  
pp. 2517-2531 ◽  
Author(s):  
B. Wolf ◽  
L. Merbold ◽  
C. Decock ◽  
B. Tuzson ◽  
E. Harris ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Temporal Resolution ◽  
Isotopic Signature ◽  
Repeated Measurements ◽  
Spectrometric Analysis ◽  
High Temporal Resolution ◽  
Site Preference ◽  
Nitrifier Denitrification ◽  
Isotopic Characterization ◽  
Intensively Managed

Abstract. The analysis of the four main isotopic N2O species (14N14N16O, 14N15N16O, 15N14N16O, 14N14N18O) and especially the intramolecular distribution of 15N ("site preference", SP) has been suggested as a tool to distinguish source processes and to help constrain the global N2O budget. However, current studies suffer from limited spatial and temporal resolution capabilities due to the combination of discrete flask sampling with subsequent laboratory-based mass-spectrometric analysis. Quantum cascade laser absorption spectroscopy (QCLAS) allows the selective high-precision analysis of N2O isotopic species at trace levels and is suitable for in situ measurements. Here, we present results from the first field campaign, conducted on an intensively managed grassland site in central Switzerland. N2O mole fractions and isotopic composition were determined in the atmospheric surface layer (at 2.2 m height) at a high temporal resolution with a modified state-of-the-art laser spectrometer connected to an automated N2O preconcentration unit. The analytical performance was determined from repeated measurements of a compressed air tank and resulted in measurement repeatability of 0.20, 0.12 and 0.11‰ for δ15Nα, δ15Nβ and δ18O, respectively. Simultaneous eddy-covariance N2O flux measurements were used to determine the flux-averaged isotopic signature of soil-emitted N2O. Our measurements indicate that, in general, nitrifier-denitrification and denitrification were the prevalent sources of N2O during the campaign and that variations in isotopic composition were due to alterations in the extent to which N2O was reduced to N2 rather than to other pathways, such as hydroxylamine oxidation. Management and rewetting events were characterized by low values of the intramolecular 15N site preference (SP), δ15Nbulk and δ18O, suggesting that nitrifier-denitrification and incomplete heterotrophic bacterial denitrification responded most strongly to the induced disturbances. The flux-averaged isotopic composition of N2O from intensively managed grassland was 6.9 ± 4.3, −17.4 ± 6.2 and 27.4 ± 3.6‰ for SP, δ15Nbulk and δ18O, respectively. The approach presented here is capable of providing long-term data sets also for other N2O-emitting ecosystems, which can be used to further constrain global N2O inventories.

INFLUENCE OF SOIL MOISTURE TENSION AND AMENDMENTS ON YIELD, OIL, AND PROTEIN CONTENT OF TARGET RAPE GROWN ON GRAY WOODED SOILS IN THE GREENHOUSE

1973 ◽  
Vol 53 (1) ◽  
pp. 87-93 ◽  
Author(s):  
W. F. NUTTALL
Keyword(s):  
Soil Moisture ◽  
Ammonium Nitrate ◽  
Protein Content ◽  
Oil Content ◽  
Fiber Content ◽  
Brassica Napus L ◽  
Available Nitrogen ◽  
Nitrate Treatment ◽  
High Soil Moisture ◽  
Loam Soil

Soil moisture tension (100 and 151 mbars) and amendments (straw, peat, manure, and ammonium nitrate) on three Gray Wooded and one Dark Gray soil significantly affected yield, oil, and protein content of Target rapeseed (Brassica napus L.). Low soil moisture tension (LSMT) gave higher yields than high soil moisture tension (HSMT). In general, lower oil content and higher protein content were obtained under HSMT than under LSMT. Also, the ammonium nitrate treatment increased protein content of the grain more than the other amendments. Protein content ranged from 28.2 to 43.3% and oil content from 38.9 to 50.0%. Regression analysis revealed that protein and oil content were inversely related (R2 = 79.6%). Lowest fiber content (highest protein plus oil) was obtained with rape grown on Dark Gray, Nipawin loam soil. Ammonium nitrate (70 μg N/g soil) produced the lowest fiber content averaged over moisture tension and soil type treatments. Those treatments that helped to increase the available nitrogen supply to the crop and that increased protein contents of the grain produced the lowest fiber contents.

scholarly journals Distinguishing Nitrous Oxide Production from Nitrification and Denitrification on the Basis of Isotopomer Abundances

2006 ◽  
Vol 72 (1) ◽  
pp. 638-644 ◽  
Author(s):  
R. L. Sutka ◽  
N. E. Ostrom ◽  
P. H. Ostrom ◽  
J. A. Breznak ◽  
H. Gandhi ◽  
...  
Keyword(s):  
Nitrogen Isotopes ◽  
Ammonia Oxidation ◽  
Nitrite Reduction ◽  
Site Preference ◽  
Ammonia Oxidizers ◽  
Site Preferences ◽  
Nitrifier Denitrification ◽  
Nitrous Oxide Production ◽  
Nitrification And Denitrification ◽  
Nitrate And Nitrite

ABSTRACT The intramolecular distribution of nitrogen isotopes in N2O is an emerging tool for defining the relative importance of microbial sources of this greenhouse gas. The application of intramolecular isotopic distributions to evaluate the origins of N2O, however, requires a foundation in laboratory experiments in which individual production pathways can be isolated. Here we evaluate the site preferences of N2O produced during hydroxylamine oxidation by ammonia oxidizers and by a methanotroph, ammonia oxidation by a nitrifier, nitrite reduction during nitrifier denitrification, and nitrate and nitrite reduction by denitrifiers. The site preferences produced during hydroxylamine oxidation were 33.5 ± 1.2‰, 32.5 ± 0.6‰, and 35.6 ± 1.4‰ for Nitrosomonas europaea, Nitrosospira multiformis, and Methylosinus trichosporium, respectively, indicating similar site preferences for methane and ammonia oxidizers. The site preference of N2O from ammonia oxidation by N. europaea (31.4 ± 4.2‰) was similar to that produced during hydroxylamine oxidation (33.5 ± 1.2‰) and distinct from that produced during nitrifier denitrification by N. multiformis (0.1 ± 1.7‰), indicating that isotopomers differentiate between nitrification and nitrifier denitrification. The site preferences of N2O produced during nitrite reduction by the denitrifiers Pseudomonas chlororaphis and Pseudomonas aureofaciens (−0.6 ± 1.9‰ and −0.5 ± 1.9‰, respectively) were similar to those during nitrate reduction (−0.5 ± 1.9‰ and −0.5 ± 0.6‰, respectively), indicating no influence of either substrate on site preference. Site preferences of ∼33‰ and ∼0‰ are characteristic of nitrification and denitrification, respectively, and provide a basis to quantitatively apportion N2O.

scholarly journals Nitrous oxide distribution and its origin in the central and eastern South Pacific Subtropical Gyre

2007 ◽  
Vol 4 (5) ◽  
pp. 729-741 ◽  
Author(s):  
J. Charpentier ◽  
L. Farias ◽  
N. Yoshida ◽  
N. Boontanon ◽  
P. Raimbault
Keyword(s):  
Nitrous Oxide ◽  
Coastal Upwelling ◽  
South Pacific ◽  
Site Preference ◽  
Natural Environments ◽  
Intermediate Water ◽  
N2o Production ◽  
South Pacific Ocean ◽  
Nitrifier Denitrification ◽  
Organic Particles

Abstract. The mechanisms of microbial nitrous oxide (N2O) production in the ocean have been the subject of many discussions in recent years. New isotopomeric tools can further refine our knowledge of N2O sources in natural environments. This study compares hydrographic, N2O concentration, and N2O isotopic and isotopomeric data from three stations along a coast-perpendicular transect in the South Pacific Ocean, extending from the center (Sts. GYR and EGY) of the subtropical oligotrophic gyre (~26° S; 114° W) to the upwelling zone (St. UPX) off the central Chilean coast (~34° S). Although AOU/N2O and NO3− trends support the idea that most of the N2O (mainly from intermediate water (200–600 m)) comes from nitrification, N2O isotopomeric composition (intramolecular distribution of 15N isotopes) expressed as SP (site preference of 15N) shows low values (10 to 12\\permil) that could be attributed to the production through of microbial nitrifier denitrification (reduction of nitrite to N2O mediated by ammonium oxidizers). The coincidence of this SP signal with high – stability layer, where sinking organic particles can accumulate, suggests that N2O could be produced by nitrifier denitrification inside particles. It is postulated that deceleration of particles in the pycnocline can modify the advection - diffusion balance inside particles, allowing the accumulation of nitrite and O2 depletion suitable for nitrifier denitrication. As lateral advection seems to be relatively insignificant in the gyre, in situ nitrifier denitrification could account for 40–50% of the N2O produced in this layer. In contrast, coastal upwelling system is characterized by O2 deficient condition and some N deficit in a eutrophic system. Here, N2O accumulates up to 480% saturation, and isotopic and isotopomer signals show highly complex N2O production processes, which presumably reflect both the effect of nitrification and denitrification at low O2 levels on N2O production, but net N2O consumption by denitrification was not observed.

scholarly journals Natural Nitrogen Isotope Ratios as a Potential Indicator of N2O Production Pathways in a Floodplain Fen

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 409
Author(s):  
Mohit Masta ◽  
Holar Sepp ◽  
Jaan Pärn ◽  
Kalle Kirsimäe ◽  
Ülo Mander
Keyword(s):  
Water Table ◽  
Isotope Composition ◽  
Nitrogen Isotope ◽  
Water Table Depth ◽  
Organic Soils ◽  
Site Preference ◽  
N2o Emissions ◽  
N2o Production ◽  
Nitrifier Denitrification ◽  
Anoxic Environment

Nitrous oxide (N2O), a major greenhouse gas and ozone depleter, is emitted from drained organic soils typically developed in floodplains. We investigated the effect of the water table depth and soil oxygen (O2) content on N2O fluxes and their nitrogen isotope composition in a drained floodplain fen in Estonia. Measurements were done at natural water table depth, and we created a temporary anoxic environment by experimental flooding. From the suboxic peat (0.5–6 mg O2/L) N2O emissions peaked at 6 mg O2/L and afterwards decreased with decreasing O2. From the anoxic and oxic peat (0 and >6 mg O2/L, respectively) N2O emissions were low. Under anoxic conditions the δ15N/δ14N ratio of the top 10 cm peat layer was low, gradually decreasing to 30 cm. In the suboxic peat, δ15N/δ14N ratios increased with depth. In samples of peat fluctuating between suboxic and anoxic, the elevated 15N/14N ratios (δ15N = 7–9‰ ambient N2) indicated intensive microbial processing of nitrogen. Low values of site preference (SP; difference between the central and peripheral 15N atoms) and δ18O-N2O in the captured gas samples indicate nitrifier denitrification in the floodplain fen.

scholarly journals Isotopic evidence for alteration of nitrous oxide emissions and producing pathways contribution under nitrifying conditions

2019 ◽  
Author(s):  
Guillaume Humbert ◽  
Mathieu Sébilo ◽  
Justine Fiat ◽  
Longqi Lang ◽  
Ahlem Filali ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Biofilm Reactor ◽  
Nitrite Reduction ◽  
Nitrous Oxide Emissions ◽  
Site Preference ◽  
N2o Emissions ◽  
Ammonium Oxidation ◽  
N2o Production ◽  
Oxidation Rates ◽  
Nitrifier Denitrification

Abstract. Nitrous oxide (N2O) emissions by a nitrifying biofilm reactor were investigated with N2O isotopocules. The site preference of N2O (15N-SP) indicated the contribution of producing and consuming pathways in response to changes in oxygenation level (from 0 to 21 % O2 in the gas mix), temperature (from 13.5 to 22.3 °C), and ammonium concentrations (from 6.2 to 62.1 mg N L−1). Nitrite reduction, either nitrifier-denitrification or heterotrophic denitrification, was the main N2O producing pathway under the tested conditions. Nitrite oxidation rates decreased as compared to ammonium oxidation rates at temperatures above 20 °C and sub-optimal oxygen levels, increasing N2O production by the nitrite reduction pathway. Below 20 °C, a difference in temperature sensitivity between hydroxylamine and ammonium oxidation rates is most likely responsible for an increase in the N2O production via the hydroxylamine oxidation pathway (nitrification). A negative correlation between the reaction kinetics and the apparent isotope fractionation was additionally shown from the variations of δ15N and δ18O values of N2O produced from ammonium.

scholarly journals Isotopic evidence for alteration of nitrous oxide emissions and producing pathways' contribution under nitrifying conditions

2020 ◽  
Vol 17 (4) ◽  
pp. 979-993
Author(s):  
Guillaume Humbert ◽  
Mathieu Sébilo ◽  
Justine Fiat ◽  
Longqi Lang ◽  
Ahlem Filali ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Biofilm Reactor ◽  
Nitrite Reduction ◽  
Nitrous Oxide Emissions ◽  
Site Preference ◽  
N2o Emissions ◽  
Ammonium Oxidation ◽  
N2o Production ◽  
Oxidation Rates ◽  
Nitrifier Denitrification

Abstract. Nitrous oxide (N2O) emissions from a nitrifying biofilm reactor were investigated with N2O isotopocules. The nitrogen isotopomer site preference of N2O (15N-SP) indicated the contribution of producing and consuming pathways in response to changes in oxygenation level (from 0 % to 21 % O2 in the gas mix), temperature (from 13.5 to 22.3 ∘C) and ammonium concentrations (from 6.2 to 62.1 mg N L−1). Nitrite reduction, either nitrifier denitrification or heterotrophic denitrification, was the main N2O-producing pathway under the tested conditions. Difference between oxidative and reductive rates of nitrite consumption was discussed in relation to NO2- concentrations and N2O emissions. Hence, nitrite oxidation rates seem to decrease as compared to ammonium oxidation rates at temperatures above 20 ∘C and under oxygen-depleted atmosphere, increasing N2O production by the nitrite reduction pathway. Below 20 ∘C, a difference in temperature sensitivity between hydroxylamine and ammonium oxidation rates is most likely responsible for an increase in N2O production via the hydroxylamine oxidation pathway (nitrification). A negative correlation between the reaction kinetics and the apparent isotope fractionation was additionally shown from the variations of δ15N and δ18O values of N2O produced from ammonium. The approach and results obtained here, for a nitrifying biofilm reactor under variable environmental conditions, should allow for application and extrapolation of N2O emissions from other systems such as lakes, soils and sediments.

Sign in / Sign up

Export Citation Format

Share Document