the Norwegian Crop Research Institute, * anne.kjersti.bakken@planteforsk.no

1. Changes in soil quality in three cropping systems after conversion from conventional to organic farming Anne Kjersti Bakken1*, Ragnar Eltun1, Trond K. Haraldsen2, Tor Arvid Breland3, Trygve S. Aamlid1 and Tore Sveistrup1 • the Norwegian Crop Research Institute, * anne.kjersti.bakken@planteforsk.no • the Norwegian Centre for Soil and Environmental Research, • (3) the Agricultural University of Norway, Department of Horticulture and Crop Sciences Model farms with 6-year crop rotations • Voll (60°N, 11°E) • Cereal and beef production on silty clay loam • Green fodder crops, two years with grass/clover leys, spring cereals, vegetables, oats • 0.9 animal units per ha • Kvithamar (63°N, 10°E) • Milk production on silty clay loam • Spring barley, three years with grass/clover ley, swede, oats • 0.10 animal units per ha • Landvik(58°N, 8°E) • Stockless production of cash crops on silt loam • Spring wheat, two years with production of clover/grass seeds, potato, lettuce, carrots • Import of composted household waste Results Analysis of soil macroporosity. Earthworm biomass in the plough layer. (Significant changes (p<0.05) at Kvithamar and Voll) Tubular macropores at 40 cm soil depth. (Significant changes (p<0.05) at Kvithamar and Voll) Content of readily available K in the plough layer. (Significant changes (p<0.05) at Landvik and Voll) • At Kvithamar and Voll the increase in the earthworm population, followed by increased soil macroporosity, might be regarded as an improvement in soil quality. This improvement was probably caused by a higher proportion of ley in the crop rotation and application of animal manure after conversion to organic farming. • The decrease in the content of readily available K at Landvik and Voll might be regarded as a deterioration in soil quality. This deterioration was the result of six year of farming with a negative K-balance (-420 and –250 kg ha-1, respectively), and deserves future concern and handling.