Nitrous oxide fluxes related to soil freeze and thaw periods identified using heat pulse probes

Abstract

. 2010. Nitrous oxide fluxes related to soil freeze and thaw periods identified using heat pulse probes. Can. J. Soil Sci. 90: 409Á418. Surface N 2 O fluxes have not been unequivocally linked to soil profile conditions, in particular the timing of water phase change. The heated needle probe is a sensor that has the potential to monitor in situ apparent volumetric heat capacity (C a ), which considers latent heat transfer, during freezing and thawing. The objective of this study was to relate the timing of N 2 O flux to the occurrence of soil water phase change between liquid and ice as determined by C a in no-tillage (NT) and conventional tillage (CT) plots monitored from fall to spring. Half-hourly micrometeorological N 2 O fluxes were measured using a tunable diode laser trace gas analyzer. Apparent heat capacity was measured at 5-cm depth using three 4-cm-long parallel needles, two equipped with thermistors and one with a heater. Two N 2 O flux events were observed for CT in January, followed by the main emission event in early March. For NT, only one emission event occurred, with lower magnitude than the CT event, and a later starting and ending date. The apparent heat capacity measured in situ with HPP showed a different temporal pattern between NT and CT, with CT presenting more phase change events. Two out of the three N 2 O emission events in CT that occurred during winter and early spring occurred immediately after phase change from ice to liquid water at 5-cm depth. The N 2 O flux associated with the phase change during the main thaw event in CT was an exponential function of the soil surface temperature increasing sharply when T!08C, but with smaller fluxes once T was!58C. The temperature response observed is consistent with the suggestion of a breakdown in the N 2 O reduction process in the 0 to 58C range, while the N 2 O production enzymes are less affected by low temperature.Key words: Nitrous oxide flux, freeze-thaw cycles, heat pulse probes, no-tillage, conventional tillage Wagner-Riddle, C., Rapai, J., Warland, J. et Furon, A. 2010. Usage de sondes a`choc thermique pour caracte´riser les flux d'oxyde nitreux associe´s au gel et au de´gel du sol. Can. J. Soil Sci. 90: 409Á418. On n'a pas relie´de fac¸on certaine les flux superficiels de N 2 O aux diffe´rentes conditions du profil du sol, surtout au moment ou`l'eau change de phase. La sonde aà iguille chauffe´e est un capteur permettant de surveiller la densite´de stockage apparente (C a ) in situ, qui tient compte du transport de calories latent lors du gel et du de´gel. L'e´tude devait associer le moment ou`survient le flux de N 2 O a`celui oul 'eau passe de l'e´tat liquide a`l'e´tat solide selon la C a , dans des parcelles non travaille´es (NT) ou travaille´es de manie`re classique (TC), examine´es de l'automne au printemps. Les flux microme´te´orologiques de N 2 O ont e´te´mesure´s de demiheure en demi-heure avec un analyseur de gaz a`l'e´tat de traces a`diode laser. La densite´de stockage apparente a e´te´e´tablie a`5 cm de profondeur graˆce ...

Modelling nitrification inhibitor effects on N<sub>2</sub>O emissions after fall- and spring-applied slurry by reducing nitrifier NH<sub>4</sub><sup>+</sup> oxidation rate

“…3c), causing greater accumulation of N 2 O s and hence greater emissions during thaw. These model findings were consistent with field observations by Congreves et al (2017) and Wagner-Riddle et al (2010) that overwinter N 2 O emissions increased with greater freezing under conventional tillage vs. no tillage, particularly with surface residue removal. Model findings were also consistent with observations by Teepe et al (2004) that N 2 O emissions during soil thawing rose sharply with increased duration of soil freezing.…”

Tillage Management and Seasonal Effects on Denitrifier Community Abundance, Gene Expression and Structure over Winter

“…It is not possible to define the exact conditions triggering the N 2 O emission rates in our study, given the limited number of sampling dates. However, other authors have reported that N 2 O emissions in winter occurred due to a temperature increase and subsequent soil thawing and influx of water from melted snow [50] and immediately after water phase change from ice to liquid water after FTEs [60].…”

The effect of nitrification inhibitors on the nitrous oxide (N2O) release from agricultural soils—a review

“…Kaiser and Ruser (2000) calculated a mean contribution of 50% of the winter fluxes to the annual N 2 O emission in various regions of Germany with distinctive frost/thaw cycles. Although the processes of enhanced N 2 O release during thawing are not completely clarified, most of the experiments reveal denitrification as the main N 2 O source ( Wagner‐Riddle et al, 2010). In addition to the thaw induced N 2 O pulses, increased flux rates have also been reported under relatively mild conditions in early winter and attributed to the turn‐over of N‐rich crop residues from cauliflowers even at low soil temperatures ( Pfab et al, 2011).…”