Table 5: Measured and estimated nitrogen flows (kg N ha−1 year−1) and selected quotients (kg N kg N−1) in the cropping systems at Apelsvoll, mean 2001–20101.

N flowCropping system2

Fertilizer applied124.9118.
Cattle slurry applied0.
Dry atmospheric depositions2.
Wet atmospheric depositions7.
N fixation by legumes0.
N in seeds12.913.
Sum field N input147.7141.648.3182.6127.5152.6

NH3 and from applied fertilizer412.511.
NH3 and from applied cattle slurry4,
Direct N2O losses41.
Drainage and runoff N 44.226.729.319.925.615.9
Sum field N output175.7140.080.2162.8149.9164.0

Field N budget−28.01.6−31.919.8−22.5−11.4

Harvested N6/applied N0.830.840.731.861.54
Drainage + runoff N /applied N0.350.230.130.450.19
Drainage + runoff N /harvested N60.430.270.670.170.240.13

1Timestep used is the agrohydrological year (May–April), thus, covering the period May 2001–April 2011.
2Each system covers 0.18 ha and consists of four rotation plots á0.045 ha.
3Including the N removed with straw. Harvested grass-clover N was reduced by 10% to account for likely harvest-related losses under practical conditions (see Section  2).
4Calculated according to [24].
5Volatilization of NH3-N from mulched clover grass is not accounted for in [24], although it may be substantial [25]. It was, therefore, calculated in accordance with Korsaeth [6].
6Not including N removed with straw.