Fixation of potassium in Finnish soils

Abstract

The fixation of potassium in Finnish soils was studied on the basis of a material consisting of 265 samples from various parts of the country. A »wet method» was employed in which 2.5 me K was added per 100 g soil, and the fixation against the extraction with neutral N ammonium acetate was determined after a period of contact of one hour. The average fixation in the 135 samples of surface soils was 0.38 ± 0.03 me K/100 g soil, and in the 130 subsoil samples 0.77 ± 0.09 me/100 g soil, or about 15 and 30 per cent of the added potassium, respectively. In the groups of the surface samples the mean values increased with the increasing content of clay from 0.25 ± 0.04 me K/100 g soil in the finesand soils to 0.56 ± 0.03 me K/100 g soil in the samples of heavy clay containing at least 60 per cent of the fraction < 2 μ. In the groups of the subsoil samples the corresponding mean values were 0.33 ± 0.24 and 1.04 ± 0.15 me K/100 g soil. In the surface soils the results ranged from 0.09 me K/100 g in a finesand soil to 1.27 me K/100 g in a clay loam, and in the subsoil samples from 0 in a sandy clay soil to 1.80 me K/100 g in one sample of clay loam and one sample of silty clay. The fixation was positively correlated with the contents of finer clay