Improving Nitrite Analysis in Soils: Drawbacks of the Conventional 2 M KCl Extraction

Homyak, Peter M.; Vasquez, Krystal; Sickman, James O.; Parker, David R.; Schimel, Joshua P.

doi:10.2136/sssaj2015.02.0061n

Cited by 25 publications

(31 citation statements)

References 36 publications

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“…a). Using an improved method for measuring NO 2 − (Homyak et al ., ), however, we show that NO 2 − can concentrate in moist soils, suggesting some substrate may indeed chemodenitrify via coupled biotic–abiotic processes (i.e., through the biological production of NO 2 − followed by its abiotic transformation to NO; Fig. a).…”

Section: Discussionmentioning

confidence: 99%

“…Soil NH 4 + and NO 3 − concentrations were measured by extraction with 2 m KCl (Maynard et al ., ), while NO 2 − was measured by extracting soils in DIW; NO 2 − was extracted in DIW because 2 m KCl underestimates NO 2 − (Stevens & Laughlin, ; Homyak et al ., ). Soil extracts were analyzed colorimetrically for NH 4 + (SEAL method EPA‐126‐A), NO 3 − (SEAL method EPA‐129‐A), and NO 2 − (SEAL method EPA‐137‐A) using a SEAL AQ‐2 discrete analyzer.…”

Section: Methodsmentioning

confidence: 99%

“…We focused on the top 5 cm because NO production is highest near the soil surface (Venterea et al, 2004). Soil cores were transported in an ice-chest to the laboratory where they were sieved (2 mm) and subsampled to determine gravimetric water content (oven drying at 104°C (Stevens & Laughlin, 1995;Homyak et al, 2015). Soil extracts were analyzed colorimetrically for NH 4 + (SEAL method EPA-126-A), NO 3 À (SEAL method EPA-129-A), and NO 2 À (SEAL method EPA-137-A) using a SEAL AQ-2 discrete analyzer.…”

Section: Soil Samplingmentioning

confidence: 99%

“…As with NO measurements, CHCl 3 -treated microcosms were kept under a CHCl 3 atmosphere at all times, except during brief periods when they were sampled. Extractable NH 4 + and NO 3 À concentrations were determined on a 5-g subsample of soil extracted in 2 M KCl as previously described, while NO 2 À was determined on a separate 5-g sample extracted in DIW (Homyak et al, 2015). Soil inorganic N concentrations are expressed as dry weight equivalent according to the soil moisture content at each sampling time.…”

Section: Laboratory Incubations: Soil N Concentrationsmentioning

confidence: 99%

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Acidity and organic matter promote abiotic nitric oxide production in drying soils

Homyak

Kamiyama

Sickman

et al. 2016

Global Change Biology

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Soils are an important source of NO, particularly in dry lands because of trade-offs that develop between biotic and abiotic NO-producing processes when soils dry out. Understanding how drier climates may offset the balance of these trade-offs as soils transition toward more arid states is, therefore, critical to estimating global NO budgets, especially because drylands are expected to increase in size. We measured NO emission pulses after wetting soils from similar lithologies along an altitudinal gradient in the Sierra Nevada, CA, where mean annual precipitation varied from 670 to 1500 mm. Along the gradient, we measured field NO emissions, and used chloroform in the laboratory to reduce microbial activity and partition between biotic and abiotic NO-producing processes (i.e., chemodenitrification). Field NO emission pulses were lowest in the acidic and SOM-rich soils (4-72 ng NO-N m s ), but were highest in the high-elevation barren site (~560 ng NO-N m s ). In the laboratory, NO emission pulses were up to 19× greater in chloroform-treated soils than in the controls, and these abiotic pulses increased with elevation as pH decreased (6.2-4.4) and soil organic matter (SOM) increased (18-157 mg C g ). Drought can shift the balance between the biotic and abiotic processes that produce NO, favoring chemodenitrification during periods when biological processes become stressed. Acidic and SOM-rich soils, which typically develop under mesic conditions, are most vulnerable to N loss via NO as interactions between pH, SOM, and drought stimulate chemodenitrification.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Soil Samplingmentioning

confidence: 99%

Section: Laboratory Incubations: Soil N Concentrationsmentioning

confidence: 99%

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Acidity and organic matter promote abiotic nitric oxide production in drying soils

Homyak

Kamiyama

Sickman

et al. 2016

Global Change Biology

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“…Based on a soil porosity of 54% (1 − ρ b /ρ s ), we expected the irrigation water to infiltrate at least 3 cm, wetting 66 NO Emission Measurements. Three months before measuring NO emissions, a polyvinylchloride collar (PVC) (30.5-cm diameter × 10-cm height) was inserted 6 cm into the ground at each of the 48 plots under vegetation and dry season length manipulations.…”

Section: −3mentioning

confidence: 99%

Aridity and plant uptake interact to make dryland soils hotspots for nitric oxide (NO) emissions

Homyak

Blankinship

Marchus

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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103

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Nitric oxide (NO) is an important trace gas and regulator of atmospheric photochemistry. Theory suggests moist soils optimize NO emissions, whereas wet or dry soils constrain them. In drylands, however, NO emissions can be greatest in dry soils and when dry soils are rewet. To understand how aridity and vegetation interact to generate this pattern, we measured NO fluxes in a California grassland, where we manipulated vegetation cover and the length of the dry season and measured [δ 15 -N]NO and [δ 18 -O]NO following rewetting with 15 N-labeled substrates. Plant N uptake reduced NO emissions by limiting N availability. In the absence of plants, soil N pools increased and NO emissions more than doubled. In dry soils, NO-producing substrates concentrated in hydrologically disconnected microsites. Upon rewetting, these concentrated N pools underwent rapid abiotic reaction, producing large NO pulses. Biological processes did not substantially contribute to the initial NO pulse but governed NO emissions within 24 h postwetting. Plants acted as an N sink, limiting NO emissions under optimal soil moisture. When soils were dry, however, the shutdown in plant N uptake, along with the activation of chemical mechanisms and the resuscitation of soil microbial processes upon rewetting, governed N loss. Aridity and vegetation interact to maintain a leaky N cycle during periods when plant N uptake is low, and hydrologically disconnected soils favor both microbial and abiotic NO-producing mechanisms. Under increasing rates of atmospheric N deposition and intensifying droughts, NO gas evasion may become an increasingly important pathway for ecosystem N loss in drylands.nitric oxide | chemodenitrification | drylands | NO pulses | N cycling N itric oxide (NO) is an important trace gas; it regulates the oxidative capacity of the atmosphere and indirectly influences Earth's climate (1). In the troposphere, NO catalyzes the production of hydroxyl radical, a powerful oxidant and cleanser of atmospheric contaminants. High concentrations of NO also favor the production of ozone (O 3 ), an urban pollutant and contributor to radiative forcing (1). Globally, fossil fuel combustion and biomass burning are major sources of NO, but soils are also a substantial source (2). Roughly 25-60% of terrestrial NO emissions originate from drylands (arid and semiarid environments) (3), which cover one-third of the terrestrial land surface (4), suggesting arid environments are important to global NO production. Climate models predict an expansion of drylands and intensifying droughts in existing arid regions (5), and when coupled with increasing rates of nitrogen (N) deposition and changes in the magnitude and frequency of precipitation events (6), increased soil NO emissions are possible (7). Paradoxically, arid soils are often described as infertile because biological processes are limited by water and N (8), raising the questions of why drylands are NO emission "hotspots."NO is produced in soils through both abiotic and biotic processes (2). Chemodeni...

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Inorganic Nitrogen diffusion in undisturbed volcanic soils during continuous drying–rewetting cycles

Clunes

Deltedesco

Pinochet

et al. 2020

J. Plant Nutr. Soil Sci.

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Background and aim: The diffusion of inorganic nitrogen (N) in soils is strongly affected by their physical characteristics and hydraulic gradients, which enable them to store and transport nutrients over time and space. The objective of this research was to use the microdialysis technique to continuously monitor the diffusive fluxes of inorganic N from the physical N store towards root surfaces in two volcanic soils after soil rewetting.Methods: Undisturbed soil samples were collected in metallic cylinders (230 cm3) at four depths (0–20, 20–40, 40–70, 70–100 cm) in two distinct volcanic soils (Andisol and Ultisol) that are used in agriculture. Diffusive N fluxes were determined during continuous drying and rewetting cycles (0 to 100 kPa) of intact undisturbed soil cores. Soil water content (SWC) at each water potential was calculated.Results and Conclusions: Diffusive fluxes increased significantly (p < 0.001) after rewetting in both soils: 16‐fold in the Andisol, from 32.7 ± 12.1 to 541.5 ± 306.5 nmol N cm−2 h−1 (34 to 62% SWC) and 66‐fold in the Ultisol, from 65.6 ± 25.8 to 4298.7 ± 1289.9 nmol N cm−2 h−1 (31 to 58% SWC) in the upper 20 cm of the soils. In addition, diffusive fluxes decreased with depth in both soils. We found that the residence time of available in these soils strongly depended upon actual SWC and thereby the functionality of the pores in the system. We propose that the ability of the porous system to transport water throughout the soil profile is a relevant parameter within N diffusion, since it allows us to estimate the increase or decrease of diffusive fluxes as a function of the soil water content during continuous drying and rewetting cycles.

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Improving Nitrite Analysis in Soils: Drawbacks of the Conventional 2 M KCl Extraction

Cited by 25 publications

References 36 publications

Acidity and organic matter promote abiotic nitric oxide production in drying soils

Acidity and organic matter promote abiotic nitric oxide production in drying soils

Aridity and plant uptake interact to make dryland soils hotspots for nitric oxide (NO) emissions

Inorganic Nitrogen diffusion in undisturbed volcanic soils during continuous drying–rewetting cycles

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