Spatial variability and hotspots of soil N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O fluxes from intensively grazed grassland

Cowan, Nelson; Norman, Prince E.; Famulari, D.; Levy, Peter E.; Reay, Dave; Skiba, U.

doi:10.5194/bg-12-1585-2015

Cited by 61 publications

(64 citation statements)

References 49 publications

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“…With respect to grasslands, no direct comparisons have been published. The intensity of grassland management and related N 2 O emissions vary widely, dependent on the rate and type of nitrogen inputs and the prevailing climate (temperature/moisture) (Cowan et al, 2015;Kelliher et al, 2017). For perennial crops planted onto intensively managed grassland, where nitrogen fertilizer and urine excretion by livestock result in high N 2 O emissions, we expect postestablishment emissions to be significantly lower, but empirical data are needed to quantify this.…”

Section: Introductionmentioning

confidence: 99%

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

et al. 2017

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Perennial bioenergy crops have significant potential to reduce greenhouse gas (GHG) emissions and contribute to climate change mitigation by substituting for fossil fuels; yet delivering significant GHG savings will require substantial land‐use change, globally. Over the last decade, research has delivered improved understanding of the environmental benefits and risks of this transition to perennial bioenergy crops, addressing concerns that the impacts of land conversion to perennial bioenergy crops could result in increased rather than decreased GHG emissions. For policymakers to assess the most cost‐effective and sustainable options for deployment and climate change mitigation, synthesis of these studies is needed to support evidence‐based decision making. In 2015, a workshop was convened with researchers, policymakers and industry/business representatives from the UK, EU and internationally. Outcomes from global research on bioenergy land‐use change were compared to identify areas of consensus, key uncertainties, and research priorities. Here, we discuss the strength of evidence for and against six consensus statements summarising the effects of land‐use change to perennial bioenergy crops on the cycling of carbon, nitrogen and water, in the context of the whole life‐cycle of bioenergy production. Our analysis suggests that the direct impacts of dedicated perennial bioenergy crops on soil carbon and nitrous oxide are increasingly well understood and are often consistent with significant life cycle GHG mitigation from bioenergy relative to conventional energy sources. We conclude that the GHG balance of perennial bioenergy crop cultivation will often be favourable, with maximum GHG savings achieved where crops are grown on soils with low carbon stocks and conservative nutrient application, accruing additional environmental benefits such as improved water quality. The analysis reported here demonstrates there is a mature and increasingly comprehensive evidence base on the environmental benefits and risks of bioenergy cultivation which can support the development of a sustainable bioenergy industry.

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Section: Introductionmentioning

confidence: 99%

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

et al. 2017

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“…The two studies described here followed a similar experimental design to that of Hodge & Fitter (2010) using dried, milled Zea mays L. leaves mixed with an agricultural soil (which had a high N 2 O production rate; Storer, 2013), to create organic matter 'patches'. These organic matter patches represent 'N 2 O hotspots' which commonly occur in natural systems (Cowan et al, 2015). Both experiments tested the hypothesis that AMF hyphae would reduce N 2 O production from the organic matter patches, while the second experiment further examined the hypothesis that a reduction in N 2 O production was a consequence of reduced nitrification rates in the presence of AMF hyphae.…”

Section: Introductionmentioning

confidence: 99%

Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N₂O hotspots

et al. 2017

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Summary Nitrous oxide (N2O) is a potent, globally important, greenhouse gas, predominantly released from agricultural soils during nitrogen (N) cycling. Arbuscular mycorrhizal fungi (AMF) form a mutualistic symbiosis with two‐thirds of land plants, providing phosphorus and/or N in exchange for carbon. As AMF acquire N, it was hypothesized that AMF hyphae may reduce N2O production. AMF hyphae were either allowed (AMF) or prevented (nonAMF) access to a compartment containing an organic matter and soil patch in two independent microcosm experiments. Compartment and patch N2O production was measured both before and after addition of ammonium and nitrate.In both experiments, N2O production decreased when AMF hyphae were present before inorganic N addition. In the presence of AMF hyphae, N2O production remained low following ammonium application, but increased in the nonAMF controls. By contrast, negligible N2O was produced following nitrate application to either AMF treatment.Thus, the main N2O source in this system appeared to be via nitrification, and the production of N2O was reduced in the presence of AMF hyphae. It is hypothesized that AMF hyphae may be outcompeting slow‐growing nitrifiers for ammonium. This has significant global implications for our understanding of soil N cycling pathways and N2O production.

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“…There is still large uncertainty associated with the quantification of N 2 O emissions released from agricultural soils on a national and global scale, due to the large spatial and temporal variability in N 2 O fluxes (Cowan et al, 2015;Jahangir et al, 2011;Mathieu et al, 2006). Many past experiments have focussed on the release of N 2 O from soils after the application of nitrogen fertilisers -which is the main cause of the rise of in N 2 O emissions since pre-industrial times (e.g.…”

Section: Introductionmentioning

confidence: 99%

The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

et al. 2016

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Abstract. Intensively managed grass production in highrainfall temperate climate zones is a globally important source of N 2 O. Many of these grasslands are occasionally tilled to rejuvenate the sward, and this can lead to increased N 2 O emissions. This was investigated by comparing N 2 O fluxes from two adjacent intensively managed grazed grasslands in Scotland, one of which was tilled. A combination of eddy covariance, high-resolution dynamic chamber and static chamber methods was used.N 2 O emissions from the tilled field increased significantly for several days immediately after ploughing and remained elevated for approximately 2 months after the tillage event contributing to an estimated increase in N 2 O fluxes of 0.85 ± 0.11 kg N 2 O-N ha −1 . However, any influence on N 2 O emissions after this period appears to be minimal. The cumulative N 2 O emissions associated with the tillage event and a fertiliser application of 70 kg N ammonia nitrate from one field were not significantly different from the adjacent untilled field, in which two fertiliser applications of 70 kg N ammonia nitrate occurred during the same period. Total cumulative fluxes calculated for the tilled and untilled fields over the entire 175-day measurement period were 2.14 ± 0.18 and 1.65 ± 1.02 kg N 2 O-N ha −1 , respectively.

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Spatial variability and hotspots of soil N<sub>2</sub>O fluxes from intensively grazed grassland

Cited by 61 publications

References 49 publications

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N₂O hotspots

The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

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Spatial variability and hotspots of soil N&lt;sub&gt;2&lt;/sub&gt;O fluxes from intensively grazed grassland

Cited by 61 publications

References 49 publications

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

Consensus, uncertainties and challenges for perennial bioenergy crops and land use

Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N2O hotspots

The influence of tillage on N&lt;sub&gt;2&lt;/sub&gt;O fluxes from an intensively managed grazed grassland in Scotland

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Spatial variability and hotspots of soil N<sub>2</sub>O fluxes from intensively grazed grassland

Arbuscular mycorrhizal fungi reduce nitrous oxide emissions from N₂O hotspots

The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland