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<p>High nitrogen (N) input is typical of irrigated intensively managed dairy pasture systems, but the plant uptake of the applied N is often low. This leads to high nitrate (NO<sub>3</sub><sup>−</sup>) accumulation in the soil which, under wet conditions, can trigger significant loss of N as nitrous oxide (N<sub>2</sub>O) and dinitrogen (N<sub>2</sub>). We investigated the effect of soil moisture [60, 80 and 100% water filled pore space (WFPS)] and NO<sub>3</sub><sup>−</sup> concentrations (45&#xa0;mg and 80&#xa0;mg NO<sub>3</sub><sup>−</sup>-N kg<sup>− 1</sup> soil) on emissions of N<sub>2</sub>O and N<sub>2</sub> by applying <sup>15</sup>NO<sub>3</sub><sup>−</sup>-N as a tracer in laboratory conditions using soil from an intensive dairy pasture. The flux of N<sub>2</sub> dominated N loss at 80% and 100% WFPS and N<sub>2</sub>O emissions were more strongly affected by NO<sub>3</sub><sup>−</sup> concentrations compared to N<sub>2</sub> emissions. N<sub>2</sub>O emissions responded more strongly to NO<sub>3</sub><sup>−</sup> concentrations at 100% WFPS than at 80% WFPS. The flux of N<sub>2</sub>O was significantly lower at 60% WFPS compared to the other WFPS levels, with no detectable N<sub>2</sub> emission. Denitrification dominated N<sub>2</sub>O emissions at 100% WFPS, whereas at 80% WFPS, contributions from denitrification and other sources were similar. These results demonstrate that while managing soil moisture and NO<sub>3</sub><sup>−</sup> availability can reduce N<sub>2</sub>O emissions in intensive dairy pastures, substantial fertiliser N losses as N<sub>2</sub> are likely to persist, limiting improvements in overall N use efficiency. </p>

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Soil nitrate concentrations increase the nitrous oxide to dinitrogen emissions ratio at high soil moisture conditions in intensive dairy pastures

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  • 发表日期：

    2026年2月3日

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  • Arjun Pandey,
  • Oxana Belyaeva,
  • Thushari Wijesinghe,
  • Helen Suter

摘要

High nitrogen (N) input is typical of irrigated intensively managed dairy pasture systems, but the plant uptake of the applied N is often low. This leads to high nitrate (NO3−) accumulation in the soil which, under wet conditions, can trigger significant loss of N as nitrous oxide (N2O) and dinitrogen (N2). We investigated the effect of soil moisture [60, 80 and 100% water filled pore space (WFPS)] and NO3− concentrations (45 mg and 80 mg NO3−-N kg− 1 soil) on emissions of N2O and N2 by applying 15NO3−-N as a tracer in laboratory conditions using soil from an intensive dairy pasture. The flux of N2 dominated N loss at 80% and 100% WFPS and N2O emissions were more strongly affected by NO3− concentrations compared to N2 emissions. N2O emissions responded more strongly to NO3− concentrations at 100% WFPS than at 80% WFPS. The flux of N2O was significantly lower at 60% WFPS compared to the other WFPS levels, with no detectable N2 emission. Denitrification dominated N2O emissions at 100% WFPS, whereas at 80% WFPS, contributions from denitrification and other sources were similar. These results demonstrate that while managing soil moisture and NO3− availability can reduce N2O emissions in intensive dairy pastures, substantial fertiliser N losses as N2 are likely to persist, limiting improvements in overall N use efficiency.