The availability and spatial distribution of oxygen (O2) in agricultural soil are controlling factors in the production and emission of nitrous oxide (N2O) to the atmosphere, but most experiments investigating the effects of various factors on N2O emissions in soil have been conducted without determining the content and distribution of O2. This complicates data interpretation and leads to speculative conclusions about which nitrogen transformation processes are responsible for N2O production. Using an O2-specific planar optode, this paper shows how spatiotemporal O2 dynamics can be used to interpret data on N2O emissions following a uniform or layered amendment of manure to agricultural soil. The spatial distribution of O2 and gas emission rates were monitored for 12 h. An anoxic layer formed rapidly around the layered manure, whereas the uniformly distributed manure led to a more widespread anoxia. Nitrous oxide emissions increased immediately after depletion of O2 in the manure-amended treatments. Greater understanding and improved knowledge of the spatial distribution of O2 is clearly beneficial and can be used to devise improved application strategies for mitigating N2O emissions from manure and other fertilizers.
Journal of Environmental Quality (online), 2014, Vol 43, Issue 5, p. 1809-1812