Properties and classification of soils of the Swedish long-term fertility experiments, 1: Sites at Fors and Kungsaengen.

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 thick dark brown coloured A-horizon and a subsoil rich in calcium carbonate and bases. Kungsaengen 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 grey, highly mottled subsoil. The Fors profile consisted of 13% clay, 42% silt (2-60 microm) and 55% sand, on average. The textural composition of the Kungsaengen 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 decreased in the Kungsaengen 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 Kungsaengen 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 Kungsaengen 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 Kungsaengen soils fixed ammonium nitrogen amounting to 0.12 and 0.49 meq NH4+-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 34-40% in the subsoil. Base saturation was troughout 100%. Base saturation in the Kungsaengen 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 (less than 10%) was found in the deeper horizons of the Fors soil but not in the Kungsaengen profile.