Capturing the Spatial Variability of N2O Emissions on Grazed Grassland.

Agricultural activities have an impact on the environment due to the application of fertilisers and management of the land. Emissions of gaseous forms of nitrogen (N) occur due to excess application, and the type of gas released will depend on environmental conditions affecting microbial processes and transport of nutrients and gases in the soil profile. Under anaerobic soil conditions, reducing processes dominate, and emissions of the non-reactive nitrous oxide (N₂O) occur; a harmful gas due to its global warming potential (≈300 that of CO₂) and its contribution to the catalytic destruction of ozone in the stratosphere.

Soil deposition of excreta from livestock result in hot spots of nutrients, particularly nitrogen (N) and carbon (C), which can be large sources of N₂O emissions. These are more intense as animals produce compaction and through urine deposition, areas of high soil moisture.

Grazed grasslands receive fertiliser N and the interaction between inorganic N and organic N and C from animal excreta can result in amplified emissions previously shown as an exponential response curve by Cardenas et al. (2010).

Measurements of N₂O emissions on grazed grasslands using chamber techniques are very challenging due to the presence of the livestock and the relatively short duration of urine patches. Techniques that are of fast response to provide spatial coverage can be very helpful to improve emission estimates, although these can be costly and labour intensive. We propose that a combination of field techniques can be used to identify hot spots of nutrients (and potential emissions).  This knowledge can be used to identify parameters that will serve as reliable proxies for N₂O emissions providing field maps with target areas for mitigation. We will present results from a spatial survey on the North Wyke Farm Platform in the South West of England.