Abstract
Fors soil (Tierp) is classified as an illitic, calcareous, frigid Udic Haploboroll according to the Soil Taxonomy and as a Calcaric Phaeozem in the FAO-system. It is a silty soil consisting of a thick dark brown coloured A-horizon and a subsoil rich in calcium carbonate and bases. Kungsängen soil (Uppsala) is classified as a fine, illitic, frigid Typic Haplaquept according to the Soil Taxonomy and as a Gleyic Cambisol in the FAO-system. It is an acid sulfate clay soil (gyttja clay) consisting of a grayish-brown A-horizon and a gray, highly mottled subsoil. The Fors profile consisted of 13% clay, 42% silt (2–60 μm) and 55% sand, on average. The textural composition of the Kungsängen profile was 57% clay, 26% silt and 17% sand. The bulk density in the Fors profile was rather constant (1.49±0.02 kg dm-3) but decresed in the Kungsängen soil below 0.6 m depth from 1.31 to 0.91 kg dm-3 due to high content of organic matter, strong aggregation and crack formation. Amounts of plant available water at a groundwater table of 1 m were 281 and 208 mm in the Fors and Kungsängen profiles, respectively. Amounts of carbon and nitrogen in the Fors soil were 111.3 tonnes C ha-1 and 10.7 tonnes N ha-1 in the A-horizon, the underlying horizons within one meter depth contained less organic material amounting to 18.2 tonnes C ha-1 and 1.7 tonnes N ha-1. However, in the Kungsängen soil more carbon and nitrogen was found in the B-horizon, amounting to 120.9 t C ha-1 and 19.2 t N ha-1, than in the A-horizon containing 78.5 t C ha-1 and 9.5 t N ha-1. The Fors and Kungsängen soils fixed ammonium nitrogen amounting to 0.12 and 0.49 meq NH+ 4-N 100 g-1 soil in the A-horizon, respectively. The calcium carbonate content was 3.5% in the A-horizon of the Fors soil and 35–40% in the subsoil. Base saturation was throughout 100%. Base saturation in the Kungsängen soil decreased from 99% in the A-horizon to 39% in the CB-horizons. The main clay mineral in both soils was found to be illite, amounting to 53–74%, followed by mixed-layer minerals. Kaolinite represented less than 10% and chlorite less than 15% in both soils. Vermiculite (<10%) was found in the deeper horizons of the Fors soil but not in the Kungsängen profile.