Nitrous oxide emission from agricultural soils

Abstract

. 1997. Nitrous oxide emission from agricultural soils. Can. J. Soil Sci. 77: [113][114][115][116][117][118][119][120][121][122][123]. A review of the salient features of N 2 O emissions from agricultural soils was done to assess our current understanding and associated problems. Nitrous oxide is an important globe warming gas and a destructive agent of ozone in the stratosphere. A major concern is the increasing contribution of chemical fertilizers to atmospheric N 2 O buildup. There is only a limited understanding of the contributions from manures, biological N 2 fixation and crop residues. A recent estimate suggests that agriculture's share of N 2 O emissions is 80% although such estimates are highly uncertain because of imprecise data and the physical and biological complexities of the production process. As a product of the nitrification and denitrification process in soils, a major problem is our understanding of the proportion of N 2 O produced, i.e. the product ratios, although there is a good general understanding of the processes involved. Measurements of N 2 O emissions from the soil surface fail to take into account N 2 O flux from the bottom of the root zone into the subsoil and aquifers although they are generally considered to be significant. There is a need to apply newly available methodology and for combining this methodology and modelling together to predict N 2 O emissions on the landscape (or field) scale taking climate, soil and cropping variables into account. There is enough information available now to exercise some control of N 2 O emissions from cultivated soils. It is suggested that this be done focusing on factors that directly affect the soil microbes involved with the nitrification (NH 4 + , O 2 ) and denitrification (NO 3 -, C, O 2 ) processes. Cropping practices and some soil characteristic amendments are suggested herein for this purpose.Key words: Denitrification, nitrification, emission control, gas ratios Beauchamp, E. G. 1997. Émission d'oxyde nitreux à partir des sols agricoles. Can. J. Soil Sci. 77: 113-123. L'auteur fait un rappel des caractères saillants des émissions de N 2 O à partir des terres agricoles et évalue l'état de nos connaissances dans ce domaine ainsi que les problèmes qui s'y rattachent. L'oxyde nitreux est un agent important du réchauffement de la planète, en plus de contribuer à la destruction de l'ozone dans la stratosphère. Particulièrement préoccupante est la contribution croissante des engrais chimiques à l'accumulation de ce gaz dans l'atmosphère. On ne comprend que partiellement la part jouée par le fumier, par la fixation biologique de N 2 et par les restes de cultures. Selon une estimation récente, 80 % des émissions de N 2 O seraient imputables à l'agriculture. Ces chiffres sont, cependant, très incertains du fait de l'imprécision des données et de la complexité des mécanismes physiques et biologiques en cause dans les processus de production. Ce qui laisse le plus à désirer, c'est notre compréhension de la proportion de N 2 O, c.-à-d. les ratio...

Overwinter soil nitrogen dynamics in seasonally frozen soils

“…Third, seasonal fluctuation in soil nitrogen is one of the variables that needs to be understood to predict the source(s) and timing of nitrate leaching beneath the root zone (DeLuca and Keeney 1994;Clay et al 1996). Seasonal N dynamics are of further interest in the context of N 2 O emissions from soil (Bochove et al 1996;Beauchamp 1997;Röver et al 1998).…”

“…The spring flush of N 2 O is thought to be produced by microbial nitrification and denitrification (Beauchamp 1997;Röver et al 1998). The most substantial release occurs during a period of a few weeks or less during spring thaw Tiedje 1990, Nyborg et al 1997;Lemke et al 1998;Röver et al 1998).…”

“…Gaseous N 2 O losses during spring thaw are significant (e.g., up to 25 kg N ha -1 ; van Bochove et al 1996;Velthof et al 1996;Nyborg et al 1997;Beauchamp 1997;Röver et al 1998). N 2 O is produced during nitrification and denitrification (Beauchamp 1997).…”

“…N 2 O is produced during nitrification and denitrification (Beauchamp 1997). Although measurements have been focussed specifically on losses of N 2 O due to its greenhouse gas propensity, losses of other forms of gaseous N (e.g., N 2 , NO, and NO 2 ) probably also occur during the same period.…”

Non‐Legume Cover Crops Can Increase Non‐Growing Season Nitrous Oxide Emissions

“…Denitrification may be enhanced in the non-growing season as freezing and thawing alters water availability, which directly controls O 2 diffusion, and stimulates microbial activity by increasing substrate solubility (Skogland et al, 1988). Cover crops could reduce N 2 O emissions because they deplete the NO 3 pool (Beauchamp, 1997;Liebig et al, 2015), the principal substrate for denitrification. Yet, there is limited information on the effect of cover crop management on N 2 O emissions during repeated freezing and thawing during the non-growing season.…”