N 2 O/ 222 Rn ‐ soil flux calibration in the stable nocturnal surface layer

Concentration changes of N 2 O and 222 Rn were monitored in the surface layer above a grass sward during the first half of two calm nights. N 2 O flux on a local or field scale was then estimated from the ratio of the concentration differences between 0.1m and 0.4m height and the directly measured 222 Rn flux. This estimate (∼7 g N 2 O‐N ha −1 d −1 ) was between the N 2 O flux on a larger scale (∼4.5 g N 2 O‐N ha −1 d −1 ), as estimated from changes in the N 2 O/ 222 Rn ratio over time, and the small scale flux on the grass plot (∼50 g N 2 O‐N ha −1 d −1 ) as measured with closed chambers.