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 flow
Cropping system2
CA1
CA2
OA
CM
OM1
OM2
Fertilizer applied
124.9
118.6
0.0
87.2
0.0
0.0
Cattle slurry applied
0.0
0.0
0.0
68.8
57.5
82.4
Dry atmospheric depositions
2.7
2.7
2.7
2.7
2.7
2.7
Wet atmospheric depositions
7.2
7.2
7.2
7.2
7.2
7.2
N fixation by legumes
0.0
0.0
34.0
14.3
57.4
59.1
N in seeds
12.9
13.1
4.4
2.5
2.6
1.1
Sum field N input
147.7
141.6
48.3
182.6
127.5
152.6
Harvest3
117.4
99.7
43.5
118.4
111.7
130.5
NH3 and from applied fertilizer4
12.5
11.9
0.0
8.7
0.0
0.0
NH3 and from applied cattle slurry4,5
0.0
0.0
6.7
13.8
11.5
16.5
Direct N2O losses4
1.6
1.7
0.7
2.1
1.0
1.1
Drainage and runoff N
44.2
26.7
29.3
19.9
25.6
15.9
Sum field N output
175.7
140.0
80.2
162.8
149.9
164.0
Field N budget
−28.0
1.6
−31.9
19.8
−22.5
−11.4
Harvested N6/applied N
0.83
0.84
—
0.73
1.86
1.54
Drainage + runoff N /applied N
0.35
0.23
—
0.13
0.45
0.19
Drainage + runoff N /harvested N6
0.43
0.27
0.67
0.17
0.24
0.13
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.