Soil Nitrous Oxide Production Research Articles

Stable Isotopes Reveal Rapid Cycling of Soil Nitrogen after Manure Application.

Understanding the fate of applied nitrogen (N) in agricultural soils is important for agronomic, environmental, and human health reasons, but it is methodologically difficult to study at the field scale. Natural abundance stable isotope measurements (δN) were used in this field study with micrometeorological measurements of nitrous oxide (NO) emissions to identify the biogeochemical processes responsible for rapid N transformations immediately after application of liquid dairy manure. Fifteen samplings occurred between 16 Mar. 2012 and 5 Apr. 2013, with a focus on spring manure application (before and after) and a winter snowmelt period. Concentrations and δN values of ammonium (NH), nitrate (NO), NO, and total N were measured throughout the year. Approximately 56 (±7)% of the NH-N applied in the spring could not be accounted for 3 d after manure application and was presumably lost by ammonia volatilization before it was tilled into the soil and/or removed from the inorganic N pool by microbial assimilation. Almost all of the remaining manure-NH (95 ± 1.1%) was converted within 3 wk to NO and NO by nitrification and nitrifier-denitrification, respectively. The in situ N isotope effect for nitrification (ε) was calculated to be -32.0 (±5.3)‰. Overall, field-scale measurements of δN at natural abundance provided valuable information that was used to distinguish sources of NH (manure vs. soil organic N) and to follow the production and consumption of NO and the pathways of NO production in soil.

Nitrous oxide production in soils and the ratio of the fungal to bacterial biomass

The proportion between the fungal and bacterial biomass, the potential activity of denitrification, and the intensity of N 2 O production were determined in the soils (chernozem and soddy-podzolic) of secondary biocenoses formed upon the abandoning of agricultural lands. The substitution of meadow and forest vegetation for agrocenoses has led to an increase in the percentage of the fungal biomass in the upper soil horizons. The rate of the net N 2 O production after the soil moistening positively correlated with the content of nitrates. In the soddy-podzolic soil (pH 3.7-5.6), the rate of nitrous oxide production was higher than that in the chernozem (pH 6.1-6.8). The rate of N 2 O production was inversely proportional to the bacterial biomass in the soils.

Freezing Effects on Carbon and Nitrogen Cycling in Northern Hardwood Forest Soils

We evaluated the effects of freeze–thaw events on soil respiration, nitrogen mineralization, nitrification, and nitrous oxide production in soils from a northern hardwood‐dominated forest in New Hampshire, USA. Soil samples from three horizons (Oe, Oa, A) from nearly monospecific stands of sugar maple (Acer saccharumMarshall) and yellow birch (Betula alleghaniensisBritton) were placed in 200‐mL incubation vessels (microlysimeters), subjected to severe (−13°C) and mild (−3°C) freeze treatments for 10 d, and then incubated at laboratory temperature (20–25°C) for 3 wk. Evolution of CO2and N2O and concentrations of leachable NH+4and NO−3were measured at weekly intervals. Freezing increased rates of C and N cycling in these soils, but the effects varied with species, horizon, and freeze treatment. Whereas severe freezing stimulated respiration, N2O flux, and mineralization, mild freezing had very few effects. Nitrification did not appear to be affected by either freeze treatment, but increases in denitrification may have masked freeze effects on this process. Freeze effects were much more marked in maple than in birch soils and in the Oaand A horizons. Maple consistently had higher rates of nitrification and N2O production than did birch. The species and horizon differences were likely driven by higher levels of available C in the birch soils and Oehorizon at both sites. These results suggest that changes in climate and snow cover that influence soil freezing could increase N and C losses from northern hardwood forest ecosystems with potential effects on soil fertility and carbon storage, receiving water quality, and atmospheric chemistry.

Snow depth, soil frost and nutrient loss in a northern hardwood forest

We have initiated a long-term experiment to examine the consequences of decreases in snowpack accumulation at the Hubbard Brook Experimental Forest (HBEF), a northern hardwood dominated forest located in the White Mountains of New Hampshire. We are quantifying the effects of decreases in snowpack accumulation on root dynamics of two key tree species in this forest (sugar maple, yellow birch), microbial biomass and activity, NO 3 - and cation loss, the acid-base chemistry of drainage water, and soil--atmosphere trace gas fluxes. We are calibrating an existing model (SNTHERM) to depict snow depth and soil frost dynamics given past or future climate scenarios for our site. In this paper, we describe the methods we are using for the manipulation studies that began in the winter of 1997/1998 and present preliminary results from our first full year of treatment. Results from our methods development efforts show that it is possible to keep plots snow free by shovelling without disturbing the forest floor. Preliminary test plot work showed that the SNTHERM model is capable of depicting snow depth and soil temperatures in both control and manipulated plots at our site. Results from our first full year of treatment showed that a relatively mild freezing event induced significant increases in nitrogen (N) mineralization and nitrification rates, solute leaching and soil nitrous oxide production and caused significant decreases in soil methane uptake. These results suggest that soil freezing events may be major regulators of soil biogeochemical processes and solute delivery to streams in forested watersheds.

Nitrous oxide production in soils cropped to corn with varying N fertilization

Mineral N fertilizers may contribute to N gas emissions to the atmosphere. Soil cores were collected in 1993 and 1994, in a sandy loam and a sandy clay cropped with an early-maturing corn (Zea mays L.) hybrid and fertilized with ammonium nitrate at rates of 10, 60, 120 or 180 kg N ha−1. Denitrification and N1O production rates, air-filled porosity (AFP), water-soluble mineral N (WSMN) and water-soluble organic C (WSOC) were measured. Denitrification and N2O production rates were generally small, but values >2 µg N2O-N kg−1 h−1 were measured (i) when WSMN contents exceeded 5 mg kg−1, and (ii) when AFP was <50 to 55% in the sandy loam, and <40 to 45% in the sandy clay. For most sampling dates, N2O production and denitrification rates increased with N fertilizer level. In 1993, AFP was relatively high and variable in soil cores, and regression analyses revealed that denitrification rates were closely related to AFP. In 1994, AFP was relatively low in soil cores, and regression analyses showed that denitrification and N2O production rates were positively related to WSMN and negatively to WSOC. It is suggested that provided AFP was low, N fertilization may have had either a direct effect on denitrification and N2O production rates by determining WSMN availability to microorganisms, or an indirect effect by affecting WSOC metabolism in soil. Depending on the year and soil type, mean denitrification rates were 40 to 130% greater in the soil with 180 than with 120 kg N ha−1. Corresponding N2O production rates were 50 to 200% higher in the 180 than in the 120 kg N ha−1 treatment. It appears that limiting N fertilizer to 120 kg ha−1, under early-maturing corn production, may prevent excessive gaseous N losses due to denitrification. Key words: Denitrification, nitrous oxide, N fertilizers, available N, grain corn

Short exposure to acetylene to distinguish between nitrifier and denitrifier nitrous oxide production in soil and sediment samples

The contribution of nitrifiers and denitrifiers to the nitrous oxide production in slurries of calcareous silt loam and river bank sediment at different oxygen concentrations was determined using acetylene as nitrification inhibitor. The addition of 10 Pa acetylene resulted in inhibition of nitrous oxide production at oxic conditions, but strongly enhanced the nitrous oxide production at oxygen-poor and anoxic conditions. Inhibition of nitrification by short exposure (1 to 24 h) to high concentrations of acetylene (100 Pa to 10 kPa) was tested using the same samples. After the removal of acetylene, nitrification was inhibited almost completely (82% to 89%) for at least 6 days whereas nitrous oxide reduction was restored within a day. It was concluded that the ‘short exposure’ inhibition method resulted in adequate nitrification inhibition without repressing the nitrous oxide reduction in anoxic nitrate-rich microsites and that the method was suitable for assessing the nitrifier contribution to the nitrous oxide emission of intact soil and sediment cores.

Short exposure to acetylene to distinguish between nitrifier and denitrifier nitrous oxide production in soil and sediment samples1

The contribution of nitrifiers and denitrifiers to the nitrous oxide production in slurries of calcareous silt loam and river bank sediment at different oxygen concentrations was determined using acetylene as nitrification inhibitor. The addition of 10 Pa acetylene resulted in inhibition of nitrous oxide production at oxic conditions, but strongly enhanced the nitrous oxide production at oxygen-poor and anoxic conditions. Inhibition of nitrification by short exposure (1 to 24 h) to high concentrations of acetylene (100 Pa to 10 kPa) was tested using the same samples. After the removal of acetylene, nitrification was inhibited almost completely (82% to 89%) for at least 6 days whereas nitrous oxide reduction was restored within a day. It was concluded that the ‘short exposure’ inhibition method resulted in adequate nitrification inhibition without repressing the nitrous oxide reduction in anoxic nitrate-rich microsites and that the method was suitable for assessing the nitrifier contribution to the nitrous oxide emission of intact soil and sediment cores.

Denitrification and nitrous oxide production in soil fallowed or under alfalfa or grass

Abstract A field study was carried out to assess the effects of agronomic practices and crops on nitrous oxide (N2O) production and denitrification rates. Air‐filled porosity, moisture content, respiration rate, and ammonium (NH4) and nitrate (NO3) concentrations were also measured along with nitrogen (N2) gas production using the static soil core procedure with acetylene (C2H2). Agronomic practices included applications of liquid cattle manure, ammonium sulfate, sucrose, and irrigation water as well as the incorporation of alfalfa. Measurements were made on fallowed soil as well as soils under alfalfa (Medicago sativa L.) and Kentucky bluegrass (Poa pratensis L.). The temporal pattern of N2 gas production was dominated by episodic events caused by manure or sucrose application, or alfalfa incorporation in conjunction with irrigation or rainfall events. Rainfall or irrigation alone did not increase N2 gas production unless following upon a dry period. In wetted soil, the N2O production rate was lower than...

Increase in nitrous oxide production in soil induced by ammonium and organic carbon

We observed that soil cores collected in the field containing relatively high NH inf4 sup+ and C substrate levels produced relatively large quantities of N2O. A series of laboratory experiments confirmed that the addition of NH inf4 sup+ and glucose to soil increase N2O production under aerobic conditions. Denitrifying enzyme activity was also increased by the addition of NH inf4 sup+ and glucose. Furthermore, NH inf4 sup+ and glocose additions increased the production of N2O in the presence of C2H2. Therefore, we concluded that denitrification was the most likely source of N2O production. Denitrification was not, however, directly affected by NH inf4 sup+ in anaerobic soil slurries, although the use of C substrate increased. In the presence of a high substrate C concentration, N2O production by denitrifiers may be affected by NO inf3 sup- supplied from NH inf4 sup+ through nitrification. Alternatively, N2O may be produced during mixotrophic and heterotrophic growth of nitrifiers. The results indicated that the NH inf4 sup+ concentration, in addition to NO inf3 sup- , C substrate, and O2 concentrations, is important for predicting N2O production and denitrification under field conditions.