Properties and Classification of Soils of the Swedish Long-Term Fertility Experiments: II. Sites at Örja and Orup

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Abstract
The Örja soil (Landskrona) was classified as a clayey, illitic, mesic Typic Eutrochrept according. to the Soil Taxonomy and as a Eutric Cambisol according to the FAO revised legend. The soil profile consisted of a dark-grayish brown coloured Ap-horizon and a slightly stony subsoil containing flint and limestones (ca. 2 vol%). The textural composition of the Örja profile was 37% clay, 35% silt (2–60 μ m) and 28% sand, on average. The bulk density was somewhat higher in the Ap-horizon (1.75 + 0.03 kg dm−3) than in the subsoil (1.62 + 0.02 kg dm−3). Assuming a groundwater table of 1 m, the amount of plant-available water was 210 mm. Amounts of carbon and nitrogen in the Örja soil were 73.8 t ha−1 and 7.4 t N ha−1 in the Ap-horizon, respectively; the subsoil contained 40.4 t C ha−1 and 7.0 t N ha−1. The Örja soils did not fix ammonium nitrogen in the plough layer. The cation exchange capacity (CEC) amounted to 18.6 meq 100 g−1 in the Ap-horizon and increased with depth to around 30 meq 100 g−1 soil. The main clay mineral found was illite, amounting to 51%, followed by smectite minerals (19–23%). Kaolinite amounted to 10% of the clay fraction, but no vermiculite was present. Assuming that Orup soil has a mollic epipedon, it was classified as a coarse-loamy, mixed frigid Aquic Haploboroll according to the Soil Taxonomy and as a Haplic Phaeozem according to the revised FAO legend. The soil profile consisted of a dark-brown coloured Ap-horizon and a massive, structureless subsoil. The profile was slightly stony, containing flint, granite and gneiss stones (about 4 vol%). The soil texture was sandy loam with 10-12% clay throughout the profile. Bulk density increased with depth from 1.61 to 1.83 kg dm−3. The compacted and structureless subsoil can limit root growth, and water uptake through roots may be restricted to the Ap-horizon holding 50 mm of plant-available water, assuming a groundwater table of 1 m. Almost all carbon and nitrogen was present in the Ap-horizon, amounting to 107.5 and 10.1 t ha−1, respectively, whereas only 2.5 t C ha−1 and 0.8 t N ha−1 were found in the subsoil. The Orup soils did not fix ammonium nitrogen in the plough layer. The CEC amounted to 15 meq 100 g−1 in the Ap-horizon and ca. 6 meq 100 g−1 in the subsoil. The clay mineralogy was as follows: The content of illite increased from 17 to 37% within the profile. Smectite minerals varied between 15 and 31%. Kaolinite increased from 5 to 15% with depth, and vermiculite (5%) was only found in the Ap-horizon.