Determining nitrous oxide emissions from subsurface measurements in grazed pasture: A field trial of alternative technology

Beneath pasture grazed by farmed animals, the soil's nitrogen (N), oxygen, and temperature regimes can be unevenly distributed in time and space. It is difficult to capture spatial and temporal variation of N2O using conventional emission measurement technology based on gas samples taken in chambers that briefly cover a small area of the soil's surface. We report the results from field deployment of alternative, non-intrusive N2O emission measurement technology that uses subsurface measurements incorporating the soil processes controlling the net N2O production and gas diffusion rates. During 100 autumn and winter days after dairy cattle urine was applied (650 kg N/ha) to freely and poorly drained pastoral soils near Hamilton, New Zealand (37.8 degrees S, 175.3 degrees E), N2O emissions were determined. The measured values ranged from 0.024 to 1.55 and 0.048 to 3.33 mg N2O-N/m(2). h for the freely and poorly drained soils, respectively. Over the 100 days, it was estimated that 0.4 and 1.3% of the applied N was directly emitted to the atmosphere as N2O from the freely and poorly drained soils, respectively.