Influence of soil moisture on codenitrification fluxes from a urea-affected pasture soil

Abstract

Intensively managed agricultural pastures contribute to N2O and N2 fluxes resulting in detrimental environmental outcomes and poor N use efficiency, respectively. Besides nitrification, nitrifier-denitrification and heterotrophic denitrification, alternative pathways such as codenitrification also contribute to emissions under ruminant urine-affected soil. However, information on codenitrification is sparse. The objectives of this experiment were to assess the effects of soil moisture and soil inorganic-N dynamics on the relative contributions of codenitrification and denitrification (heterotrophic denitrification) to the N2O and N2 fluxes under a simulated ruminant urine event. Repacked soil cores were treated with 15N enriched urea and maintained at near saturation (−1 kPa) or field capacity (−10 kPa). Soil inorganic-N, pH, dissolved organic carbon, N2O and N2 fluxes were measured over 63 days. Fluxes of N2, attributable to codenitrification, were at a maximum when soil nitrite (NO2−) concentrations were elevated. Cumulative codenitrification was higher (P = 0.043) at −1 kPa. However, the ratio of codenitrification to denitrification did not differ significantly with soil moisture, 25.5 ± 15.8 and 12.9 ± 4.8% (stdev) at −1 and −10 kPa, respectively. Elevated soil NO2− concentrations are shown to contribute to codenitrification, particularly at −1 kPa.

Soil‐Gas Diffusivity and Soil‐Moisture effects on N2O Emissions from Intact Pasture Soils

“…Microbial transformation of the N inputs to pasture soils result in N 2 O production. These transformation pathways include nitrification, nitrifier-denitrification, codenitrification, and denitrification (Wrage-Mönnig et al, 2018;Clough et al, 2017;Kool et al, 2011). In anoxic environments, denitrification dominates formation of N 2 O, and if the process goes to completion N 2 O is reduced to N 2 (Firestone, 1982).…”

Microbial pathways for nitrogen loss in an upland soil

“…In the N 2 produced from codenitrification process, one N atom from the reduced NO 2 2 and the other N atom from nucleophiles compounds [i.e., azide (N 1 3 ), ammonia (NH 3 ), salicylhydroxamic acid (C 7 H 7 NO 3 ) and hydroxylamine (NH 2 OH)], thereby being different from denitrification. Co-denitrification may occur in fungi, bacteria or archaea, which has been detected in grassland and agricultural soils (Laughlin and Stevens, 2002;Spott and Strange, 2011;Long et al, 2013;Selbie et al, 2015;Xi et al, 2016;Clough et al, 2017). However, the occurrence of co-denitrification prefers (i) anaerobic condition, (ii) neutral pH 6.0-7.5, (iii) low availability of respirable organic carbon substrates and (iv) high ratio between potential nucleophiles and NO 2 2 (Spott and Strange, 2011;Lewicka-Szczebak et al, 2016).…”

CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O fluxes along an altitudinal gradient in the northern Ecuadorean Andes: N<sub>2</sub>O consumption at higher altitudes

“…nitrification, nitrifier-denitrification, chemodenitrification, etc. ;(Butterbach-Bahl et al, 2013;van Cleemput, 1998;Clough et al, 2017)). Overall, tropical forests emit on average 12.1 t CO2-C ha -1 y -1 (heterotrophic 55 and autotrophic respiration), slightly smaller than the Net Primary Productivity (NPP) (12.5 t CO2-C ha -1 y -1 ) i.e.…”