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The overall objective of this study was to discover the most limiting soil properties for crop production at two fertility sites. The Vreta Kloster soil, classified as a very fine, mixed, semiactive Oxyaquic Haplocryoll, according to the Soil Taxonomy and as a Haplic Phaeozem according to the World Reference Base for Soil Resources (WRB), consisted of very dark greyish brown silty clay overlying a subsoil of heavy clay (70-80%). Porosity increased with depth due to a greater micro- but not macro-pore volume. Stocks of C and N amounted to 76.4 t C ha-¹ and 8.7 t N ha-¹ in the Ap-horizon and 24.8 t C ha-¹ and 3.25 t N ha-¹ in the subsoil to 1 m depth. Soil pH increased with depth, 6.6 to 7.4, and CEC values ranged 25 to 31 cmo1c kg-¹ soil. The main clay minerals were illite/mica (45%) followed by vermiculite (9-20%). Chlorite and kaolinite amounted to 2% throughout the profile. In dry years, crop production at the Vreta Kloster site was greatly reduced, which can be attributed to the absence of macro-pores and high portion of micro-pores and in the subsoil reducing the amount of water available to crops. The Högåsa profile, classified as a sandy mixed Humic Dystrocryept according to the Soil Taxonomy and as Arenic Umbrisol according WRB, consisted of loamy very fine and fine sand. Soil pH and bulk density increased with depth from 5.7 to 6.5 and 1.3 to 1.6 kg dm-³, respectively. Carbon and N stocks amounted to 72.3 t C ha-¹ and 5.9 t N ha-¹ in the Ap-horizon and were low in the subsoil, 13.5 t C ha-¹ and 1.1 t N ha-¹. Clay mineralogy was dominated by illite/mica (26-50%) with vermiculite being formed in the Ap-horizon. Chlorite amounted to 3-6% and kaolinite to 2-3% in the profile. Crop yields were less affected by rainfall conditions and leys were more productive at Högåsa than Vreta Kloster. A high mechanical resistance reducing root penetration of the subsoil and a low nutrient content limited crop production at Högåsa. [ABSTRACT FROM AUTHOR]

The Ekebo soil was classified as a coarse-loamy, mixed, mesic Oxyaquic Hapludoll according to the Soil Taxonomy and as a Haplic Phaeozem according to the World Reference Base for Soil Resources (WRB). The soil profile consisted of a very dark greyish brown Ap-horizon over a compact subsoil with porosity and permeability decreasing with depth. The textural composition of the Ekebo profile was almost uniform, with 19% clay, 36% silt (2-60 μm) 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[sup -1] 6.1 t N ha[sup -1] in the Ap-horizon, respectively, and the subsoil to 1 m contained 34 t C ha[sup -1] and 3.3 t N ha[sup -1]. The sum of cations amounted to 8.7 cmol[sub c] kg[sup -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 concentrations of 25-39% throughout the profile, followed by illite, 19-31%. Vermiculite amounted to 2-7% and kaolinite to 2-5% while chlorite was only present in the topsoil. The Fjärdingslöv 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 very 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 10-20% clay. The bulk density increased with depth from 1.60 to 1.87 kg dm[sup -3]. Carbon and nitrogen present in the Ap-horizon amounted to 61 t C ha[sup -1] and 6.2 t N ha[sup -1], and 30 t C ha[sup -1] and 3.8 t N ha[sup -1] were found in the subsoil. The cation-exchange capacity amounted to 12.1 cmol[sub c] kg[sup -1] soil in the Ap-horizon and was somewhat lower in the subsoil. The clay mineralogy 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%, chlorite to 2% and kaolinite to about 1% in the profile. Although both soils ended up as Hapludolls in the classification, there are differences in productivity. Fjärdingslöv produces somewhat higher yields. Owing to the fact that several Swedish agricultural soils are classified as Mollisols but their character is more similar to Inceptisols, a revision of the required characteristics for a mollic epipedon is discussed. [ABSTRACT FROM AUTHOR]