Measured and modelled estimates of nitrous oxide emission and methane consumption from a sheep-grazed pasture

Saggar, Surinder; Hedley, C. B.; Giltrap, Donna; Lambie, Suzanne

doi:10.1016/j.agee.2007.02.006

Cited by 123 publications

(52 citation statements)

References 19 publications

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“…The low emission factors found in the present study may have been caused by the relatively dry soil conditions that prevailed during the study. Low emission factors have been previously observed above sheep-grazed pastures under dry summer months, with maximum emissions occurring under cooler and wetter soil conditions (Allen et al 1996;Saggar et al 2007). Rainfall and soil drainage class have been identified as key variables influencing N 2 O emission factors from urine returns (de Klein et al 2003), and a consideration of environmental and management factors (which are not considered in the IPCC Tier 1 approach) will undoubtedly be important for better constraining N 2 O emission estimates from grazed soils.…”

Section: Discussionmentioning

confidence: 99%

Disentangling the effect of sheep urine patch size and nitrogen loading rate on cumulative N2O emissions

2016

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Abstract. Ruminant urine nitrogen (N) concentration and volume are important parameters influencing the size and N loading rate of urine patches deposited to soil. Such parameters can influence N cycling and emissions of the greenhouse gas, nitrous oxide (N 2 O) from grazed grassland, yet, there is limited information on the effect of these parameters within typical ranges reported for sheep. We used an automated, high-frequency gas monitoring system to investigate N 2 O emissions from varying urine N application rates and patch sizes under field conditions. Using artificial sheep urine, we manipulated urine N concentration to provide two urine N application rates (4 and 16 g N/L; equivalent to 200 and 800 kg N/ha). We investigated the effect of urine patch size with equal N application rates (4 · 125 cm 2 vs 500 cm 2 , at 200 and 800 kg N/ha) and the effect of patch size with unequal N application rates, but the same total amount of N applied (62.5 mL over 125 cm 2 at 800 kg N/ha and 250 mL over 500 cm 2 at 200 kg N/ha). Cumulative emissions of N 2 O generally increased with N loading rate, whether applied as one large urine patch or four smaller ones. Cumulative N 2 O emissions increased when the N was applied in four smaller urine patches compared with one large patch; this difference was significant at 800 kg N/ha, but not at 200 kg N/ha. When the total amount of N applied was held constant (1 g of N), the amount of N 2 O released was similar when urine was applied as a high N concentration small patch (800 kg N/ha) compared with a low N concentration large patch (200 kg N/ha). Urine N 2 O emission factors in this study were, on average, 10 times lower than the IPCC default of 1% for sheep excreta. This research clearly demonstrates that the chemical and physical nature of the urine patch influences N 2 O emissions, yet further research is required to gather more data on typical sheep urine volumes (individual and daily), urination frequency, urine N concentrations and the typical volumes of soil influenced by urine deposition, to provide more accurate estimates of emissions from sheep grazed pastures.

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Section: Discussionmentioning

confidence: 99%

Disentangling the effect of sheep urine patch size and nitrogen loading rate on cumulative N2O emissions

2016

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“…ΔC/Δt is the slope of the line for T 0 and T 40 (Saggar et al, 2007), ΔC is the change in gas concentration in the chamber headspace during the enclosure period in ppbv, Δt is the …”

Section: N 2 O Measurement and Sample Analysismentioning

confidence: 99%

Reducing nitrous oxide emissions by changing N fertiliser use from calcium ammonium nitrate (CAN) to urea based formulations

Harty

Forrestal

Watson

et al. 2016

Science of The Total Environment

144

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*Corresponding authors karl.richards@teagasc.ieHighlights  The N 2 O emission factor for CAN was substantially higher than the IPCC default and highly variable between sites and across years. Urea products decreased direct N 2 O emissions from CAN on average by 80%  Switching from CAN to urea products reduces both N 2 O emissions and fertiliser costs. 3 AbstractThe accelerating use of synthetic nitrogen (N) fertilisers, to meet the world's growing food demand, is the primary driver for increased atmospheric concentrations of nitrous oxide (N 2 O). The IPCC default emission factor (EF) for N 2 O from soils is 1% of the N applied, irrespective of its form. However, N 2 O emissions tend to be higher from nitrate-containing fertilisers e.g. calcium ammonium nitrate (CAN) compared to urea, particularly in regions, which have mild, wet climates and high organic matter soils. Urea can be an inefficient N source due to NH 3 volatilisation, but nitrogen stabilisers (urease and nitrification inhibitors) can improve its efficacy. This study evaluated the impact of switching fertiliser formulation from calcium ammonium nitrate (CAN) to urea-based products, as a potential mitigation strategy to reduce N 2 O emissions at six temperate grassland sites on the island of Ireland. The surface applied formulations included CAN, urea and urea with the urease inhibitor N-(nbutyl) thiophosphoric triamide (NBPT) and/or the nitrification inhibitor dicyandiamide (DCD). Results showed that N 2 O emissions were significantly affected by fertiliser formulation, soil type and climatic conditions. The direct N 2 O emission factor (EF) from CAN averaged 1.49% overall sites, but was highly variable, ranging from 0.58% to 3.81.Amending urea with NBPT, to reduce ammonia volatilisation, resulted in an average EF of 0.40% (ranging from 0.21 to 0.69%)-compared to an average EF of 0.25% for urea (ranging from 0.1 to 0.49%), with both fertilisers significantly lower and less variable than CAN.Cumulative N 2 O emissions from urea amended with both NBPT and DCD were not significantly different from background levels. Switching from CAN to stabilised urea formulations was found to be an effective strategy to reduce N 2 O emissions, particularly in wet, temperate grassland. 4Key words nitrous oxide mitigation; emission factor; calcium ammonium nitrate; stabilised urea; nitrification inhibitor Dicyandiamide (DCD); urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT).5

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“…Saggar et al (2007) produced a modified version (the denitrification-decomposition model for New Zealand -NZ-DNDC) of DNDC (Li et al, 2000) to evaluate local impacts of changes in climate, soil properties, fertilizer management and grazing regimes on soil methanotrophy. Sabrekov et al (2016) developed a process-based model of soil CH 4 uptake that also incorporates rhizosphere methanotrophy.…”

Section: Introductionmentioning

confidence: 99%

Soil Methanotrophy Model (MeMo v1.0): a process-based model to quantify global uptake of atmospheric methane by soil

et al. 2018

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Abstract. Soil bacteria known as methanotrophs are the sole biological sink for atmospheric methane (CH 4 ), a potent greenhouse gas that is responsible for ∼ 20 % of the humandriven increase in radiative forcing since pre-industrial times. Soil methanotrophy is controlled by a plethora of factors, including temperature, soil texture, moisture and nitrogen content, resulting in spatially and temporally heterogeneous rates of soil methanotrophy. As a consequence, the exact magnitude of the global soil sink, as well as its temporal and spatial variability, remains poorly constrained. We developed a process-based model (Methanotrophy Model; MeMo v1.0) to simulate and quantify the uptake of atmospheric CH 4 by soils at the global scale. MeMo builds on previous models by Ridgwell et al. (1999) and Curry (2007) by introducing several advances, including (1) a general analytical solution of the one-dimensional diffusion-reaction equation in porous media, (2) a refined representation of nitrogen inhibition on soil methanotrophy, (3) updated factors governing the influence of soil moisture and temperature on CH 4 oxidation rates and (4) the ability to evaluate the impact of autochthonous soil CH 4 sources on uptake of atmospheric CH 4 . We show that the improved structural and parametric representation of key drivers of soil methanotrophy in MeMo results in a better fit to observational data. A global simulation of soil methanotrophy for the period 1990-2009 using MeMo yielded an average annual sink of 33.5 ± 0.6 Tg CH 4 yr −1 . Warm and semi-arid regions (tropical deciduous forest and open shrubland) had the highest CH 4 uptake rates of 602 and 518 mg CH 4 m −2 yr −1 , respectively. In these regions, favourable annual soil moisture content (∼ 20 % saturation) and low seasonal temperature variations (variations < ∼ 6 • C) provided optimal conditions for soil methanotrophy and soil-atmosphere gas exchange. In contrast to previous model analyses, but in agreement with recent observational data, MeMo predicted low fluxes in wet tropical regions because of refinements in formulation of the influence of excess soil moisture on methanotrophy. Tundra and mixed forest had the lowest simulated CH 4 uptake rates of 176 and 182 mg CH 4 m −2 yr −1 , respectively, due to their marked seasonality driven by temperature. Global soil uptake of atmospheric CH 4 was decreased by 4 % by the effect of nitrogen inputs to the system; however, the direct addition of fertilizers attenuated the flux by 72 % in regions with high agricultural intensity (i.e. China, India and Europe) and by 4-10 % in agriculture areas receiving low rates of N input (e.g. South America). Globally, nitrogen inputs reduced soil uptake of atmospheric CH 4 by 1.38 Tg yr −1 , which is 2-5 times smaller than reported previously. In addition to improved characterization of the contemporary soil sink for atmospheric CH 4 , MeMo provides an opportunity to quantify more accurately the relative importance of soil methanotrophy in the global CH 4 cycle in the past and its capaci...

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Measured and modelled estimates of nitrous oxide emission and methane consumption from a sheep-grazed pasture

Cited by 123 publications

References 19 publications

Disentangling the effect of sheep urine patch size and nitrogen loading rate on cumulative N2O emissions

Disentangling the effect of sheep urine patch size and nitrogen loading rate on cumulative N2O emissions

Reducing nitrous oxide emissions by changing N fertiliser use from calcium ammonium nitrate (CAN) to urea based formulations

Soil Methanotrophy Model (MeMo v1.0): a process-based model to quantify global uptake of atmospheric methane by soil

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