N, P, and K Budgets and Changes in Selected Topsoil Nutrients over 10 Years in a Long-Term Experiment with Conventional and Organic Crop Rotations

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 system^2
	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
Harvest^3	117.4	99.7	43.5	118.4	111.7	130.5
NH3 and NO𝑥 from applied fertilizer^4	12.5	11.9	0.0	8.7	0.0	0.0
NH3 and NO𝑥 from applied cattle slurry^4,5	0.0	0.0	6.7	13.8	11.5	16.5
Direct N2O losses^4	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 N^6/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 N^6	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.