A new conceptual framework explaining spatial variation in soil nitrous oxide emissions

Soil emissions of nitrous oxide (N 2 O), a potent greenhouse gas, contribute substantially to global warming from agriculture. Spatial variation in N 2 O emissions within agricultural fields leads to high uncertainty in the benefits of climate-smart agricultural practices. Here, we present a new conceptual framework explaining spatial variation in soil N 2 O emissions developed from high spatial resolution automated measurements of soil N 2 O emissions together with measurements of gross N 2 O fluxes and soil physicochemical properties in two separately managed maize fields in central Illinois, USA. We found that sub-field locations with consistently low N 2 O emissions had distinct biogeochemical properties compared to locations where high emissions occurred episodically, leading to spatial variation in which factors control N 2 O production rates. In the consistent N 2 O cold spots, soil nitrate (NO 3 - ) and dissolved organic carbon (DOC) constrained N 2 O production irrespective of changes in soil moisture. In contrast, in the episodic N 2 O hot spots which had higher soil NO 3 - and DOC availability, N 2 O production was stimulated by increases in soil moisture. These findings form the ‘cannon model’ which conceptualizes how sub-field scale variation in soil NO 3 - and DOC determines where increases in soil moisture can trigger high soil N 2 O emissions within agricultural fields.