Properties and classification of soils of the Swedish long-term fertility experiments - IV. Sites at Ekebo and Fjardingslov

The Ekebo soil was classified as a coarse-loamy, mixed, mesic Oxyaquic Hapl udoll according to the Soil Taxonomy and as a Haplic Phaeozem according to the World Reference Base for Soil Resources (WRB). The soil profile consist ed of a very dark greyish brown Ap-horizon over a compact subsoil with poro sity and permeability decreasing with depth. The textural composition of th e Ekebo profile was almost uniform, with 19% clay, 36% silt (2-60 mu m) and 45% sand, on average, but an increasing content of stones and gravel up to 15% with depth. Amounts of carbon and nitrogen in the Ekebo soil were 90 t C ha(-1) 6.1 t N ha(-1) in the Ap-horizon, respectively, and the subsoil t o 1 m contained 34 t C ha(-1) and 3.3 t N ha(-1) The sum of cations amounte d to 8.7 cmol(c) kg(-1) soil in the Ap-horizon and 6.8 in the subsoil, The main clay minerals in the Ekebo soil were mixed-layer minerals showing conc entrations of 25-39% throughout the profile, followed by illite, 19-31%. Ve rmiculite amounted to 2-7% and kaolinite to 2-5% while chlorite was only pr esent in the topsoil. The Fjardingslov soil was also classified as a coarse -loamy, mixed, mesic Oxyaquic hapludoll according the Soil Taxonomy and as a Haplic Phaeozem according to WRB. The soil profile consisted of a thick v ery greyish brown A-horizon over a subsoil with calcium carbonate content ( 0.13-14.9%) increasing with depth. The soil texture was a sandy loam with 1 0-20% clay. The bulk density increased with depth from 1.60 to 1.87 kg dm(- 3). Carbon and nitrogen present in the Ap-horizon amounted to 61 t C ha(-1) and 6.2 t N ha(-1), and 30 t C ha(-1) and 3.8 t N ha(-1) were found in the subsoil. The cation-exchange capacity amounted to 12.1 cmol(c) kg(-1) soil in the Ap-horizon and was somewhat lower in the subsoil. The clay mineralo gy was as follows. The content of mixed-layer minerals was higher than that of illite in the top and upper subsoil. Vermiculite amounted to 6-10%, chl orite to 2% and kaolinite to about 1% in the profile. Although both soils e nded up as Hapludolls in the classification, there are differences in produ ctivity. Fjardingslov produces somewhat higher yields. Owing to the fact th at several Swedish agricultural soils are classified as Mollisols but their character is more similar to Inceptisols, a revision of the required chara cteristics for a mollic epipedon is discussed.