Can pH amendments in grazed pastures help reduce N2O emissions from denitrification? – The effects of liming and urine addition on the completion of denitrification in fluvial and volcanic soils

McMillan, Andrew M. S.; Pal, Pranoy; Phillips, R.; Palmada, Thilak; Berben, Peter H.; Jha, Neha; Saggar, Surinder; Luo, Jiafa

doi:10.1016/j.soilbio.2015.10.013

Cited by 68 publications

(34 citation statements)

References 35 publications

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“…Consequently, where and when it occurs, denitrification in allophanic soils is likely to lead to significant N 2 O emissions. This result fits with other work from our group, which indicates that allophanic soils emit greater N 2 O : (N 2 O + N 2 ) relative to other soil types (McMillan et al, 2016). Taken together, these results suggest that targeted management of nirS denitrifiers in allophanic soils during wet seasons may be an effective strategy to combat greenhouse gas emissions from pastoral agriculture in volcanic regions.…”

Section: Discussionsupporting

confidence: 91%

Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture

et al. 2017

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Abstract. Denitrification is an anaerobic respiration process that is the primary contributor of the nitrous oxide (N 2 O) produced from grassland soils. Our objective was to gain insight into the relationships between denitrifier community size, structure, and activity for a range of pasture soils. We collected 10 dairy pasture soils with contrasting soil textures, drainage classes, management strategies (effluent irrigation or non-irrigation), and geographic locations in New Zealand, and measured their physicochemical characteristics. We measured denitrifier abundance by quantitative polymerase chain reaction (qPCR) and assessed denitrifier diversity and community structure by terminal restriction fragment length polymorphism (T-RFLP) of the nitrite reductase (nirS, nirK) and N 2 O reductase (nosZ) genes. We quantified denitrifier enzyme activity (DEA) using an acetylene inhibition technique. We investigated whether varied soil conditions lead to different denitrifier communities in soils, and if so, whether they are associated with different denitrification activities and are likely to generate different N 2 O emissions. Differences in the physicochemical characteristics of the soils were driven mainly by soil mineralogy and the management practices of the farms. We found that nirS and nirK communities were strongly structured along gradients of soil water and phosphorus (P) contents. By contrast, the size and structure of the nosZ community was unrelated to any of the measured soil characteristics. In soils with high water content, the richnesses and abundances of nirS, nirK, and nosZ genes were all significantly positively correlated with DEA. Our data suggest that management strategies to limit N 2 O emissions through denitrification are likely to be most important for dairy farms on fertile or allophanic soils during wetter periods. Finally, our data suggest that new techniques that would selectively target nirS denitrifiers may be the most effective for limiting N 2 O emissions through denitrification across a wide range of soil types.

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Section: Discussionsupporting

confidence: 91%

Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture

et al. 2017

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“…These data suggest that N 2 O was not consumed during the incubation and both gases were produced independently. This finding contrasts with bacterial denitrification22, where a sharp rise in microbial production of N 2 O is followed by a rise in biological reduction of N 2 O to N 2 , and a drop in cumulative N 2 O production21. Bipolaris sorokiniana denitrifies NO 2 − only and does not use glutamine to form N 2 O16.…”

Section: Resultsmentioning

confidence: 78%

“…The role of N 2 O in the codenitrification process and in N 2 formation is not clear20. While utilisation of N 2 O to form N 2 has been suggested as a plausible codenitrification pathway8, reports of N 2 O consumption during fungal production of N 2 (commonly observed during bacterial denitrification)21 are lacking. Potentially bypassing reduction of N 2 O to form N 2 , in addition to formation of hybrid N 2 , sets codenitrification and anammox apart from classical denitrification22.…”

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confidence: 99%

“…Oxygen status was tightly controlled with airtight laboratory incubation vessels, where headspace was filled with either helium (anaerobic) or heliox (aerobic). Accumulation of headspace O 2 , CO 2 , N 2 O, and N 2 were measured approximately every 6 h with a customised, robotic gas chromatography system21. Headspace O 2 was monitored to confirmed anaerobiosis was maintained during the 30 h incubation.…”

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confidence: 99%

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Chemical formation of hybrid di-nitrogen calls fungal codenitrification into question

Phillips

Song²,

McMillan

et al. 2016

Sci Rep

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Removal of excess nitrogen (N) can best be achieved through denitrification processes that transform N in water and terrestrial ecosystems to di-nitrogen (N2) gas. The greenhouse gas nitrous oxide (N2O) is considered an intermediate or end-product in denitrification pathways. Both abiotic and biotic denitrification processes use a single N source to form N2O. However, N2 can be formed from two distinct N sources (known as hybrid N2) through biologically mediated processes of anammox and codenitrification. We questioned if hybrid N2 produced during fungal incubation at neutral pH could be attributed to abiotic nitrosation and if N2O was consumed during N2 formation. Experiments with gas chromatography indicated N2 was formed in the presence of live and dead fungi and in the absence of fungi, while N2O steadily increased. We used isotope pairing techniques and confirmed abiotic production of hybrid N2 under both anoxic and 20% O2 atmosphere conditions. Our findings question the assumptions that (1) N2O is an intermediate required for N2 formation, (2) production of N2 and N2O requires anaerobiosis, and (3) hybrid N2 is evidence of codenitrification and/or anammox. The N cycle framework should include abiotic production of N2.

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“…This suggests pH is part of a universally conserved mechanism selecting for both emissions and microbial communities. The range of pH observed in our soils (5.57–7.03) was sufficient to capture the range at which the N 2 O reductase and N 2 O emissions fluctuate in response to pH26444546. Soil pH controls not only the assembly of the N 2 O reductase2627, but also alters general expression patterns24 and selects for shifts in microbial community composition31 indirectly influencing the abundance and type of functional genes in soils.…”

Section: Discussionmentioning

confidence: 99%

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

Samad

Biswas

Bakken

et al. 2016

Sci Rep

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Denitrification is mediated by microbial, and physicochemical, processes leading to nitrogen loss via N2O and N2 emissions. Soil pH regulates the reduction of N2O to N2, however, it can also affect microbial community composition and functional potential. Here we simultaneously test the link between pH, community composition, and the N2O emission ratio (N2O/(NO + N2O + N2)) in 13 temperate pasture soils. Physicochemical analysis, gas kinetics, 16S rRNA amplicon sequencing, metagenomic and quantitative PCR (of denitrifier genes: nirS, nirK, nosZI and nosZII) analysis were carried out to characterize each soil. We found strong evidence linking pH to both N2O emission ratio and community changes. Soil pH was negatively associated with N2O emission ratio, while being positively associated with both community diversity and total denitrification gene (nir & nos) abundance. Abundance of nosZII was positively linked to pH, and negatively linked to N2O emissions. Our results confirm that pH imposes a general selective pressure on the entire community and that this results in changes in emission potential. Our data also support the general model that with increased microbial diversity efficiency increases, demonstrated in this study with lowered N2O emission ratio through more efficient conversion of N2O to N2.

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Can pH amendments in grazed pastures help reduce N2O emissions from denitrification? – The effects of liming and urine addition on the completion of denitrification in fluvial and volcanic soils

Cited by 68 publications

References 35 publications

Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture

Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture

Chemical formation of hybrid di-nitrogen calls fungal codenitrification into question

Phylogenetic and functional potential links pH and N2O emissions in pasture soils

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