Journal Article

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

Richards, KG, de Klein, CAM, Johns, C, Bakken, LR, Condron, LM, Clough, Timothy, Samad, MS, Rex, D, Grant, J, Lanigan, GJ, Morales, SE

2017

Overview

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.

• Publisher: Nature Publishing Group,Nature Publishing Group UK,Nature Portfolio
• Subject: 704/106/47/4112 / 704/47/4112 / Cores / Denitrification / Dissolved organic carbon / Field capacity / Humanities and Social Sciences / multidisciplinary / Nitrification / Nitrogen dioxide / Nitrous oxide / Pasture / pH effects / Science / Science (multidisciplinary) / Soil moisture / Urea / Urine