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 7

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

K flow	Cropping system^2
	CA1	CA2	OA	CM	OM1	OM2
Fertilizer	90.7	88.4	0.0	56.9	0.0	0.0
Cattle slurry applied	0.0	0.0	0.0	89.2	74.7	101.8
Wet atmospheric depositions	2.1	2.1	2.1	2.1	2.1	2.1
K in seeds	11.4	11.4	0.9	0.6	0.6	0.3
Sum field K input	104.2	101.9	3.0	148.8	77.4	104.2
Harvested K^3	70.4	46.8	9.3	101.4	82.2	112.0
Drainage and runoff K	6.6	4.1	3.3	3.6	3.3	2.3
Sum field K output	77.0	50.9	12.6	105.1	85.4	114.3
Field K budget	27.2	51.0	−9.7	43.7	−8.0	−10.1
Harvested K^4/applied K	0.53	0.53		0.66	1.04	1.05
Drainage + runoff K/applied K	0.07	0.05		0.03	0.04	0.02
Drainage + runoff K/harvested K^4	0.14	0.09	0.36	0.04	0.04	0.02

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 K removed with straw. Harvested grass-clover K was reduced by 10% to account for likely harvest-related losses under practical conditions (see Section 2).
⁴Not including K removed with straw.