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 6

Measured and estimated phosphorus flows (kg P ha⁻¹ year⁻¹) and selected quotients (kg P kg P⁻¹) in the cropping systems at Apelsvoll, mean 2001–2010¹.

P flow	Cropping system^2
	CA1	CA2	OA	CM	OM1	OM2
Fertilizer	29.8	29.5	0.0	15.0	0.0	0.0
Cattle slurry applied	0.0	0.0	0.0	9.6	7.9	10.9
P in seeds	2.6	2.7	0.7	0.5	0.5	0.2
Sum field P input	32.5	32.1	0.7	25.1	8.4	11.1
Harvested P^3	24.1	20.5	8.8	21.0	18.2	20.7
Drainage and runoff P	0.2	0.1	0.2	0.3	0.2	0.2
Sum field P output	24.3	20.7	8.9	21.2	18.4	20.9
Field P budget	8.2	11.5	−8.2	3.9	−10.0	−9.8
Harvested P^4/applied P	0.72	0.70		0.82	2.17	1.82

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 á 0.045 ha.
³Including the P removed with straw. Harvested grass-clover P was reduced by 10% to account for likely harvest-related losses under practical conditions (see Section  2).
⁴Not including P removed with straw.