The Long-Term Soil Fertility Experiments in Southern Sweden

Ten cuttings of perennial ryegrass were taken from a pot trial with soils from the Long-Term Soil Fertility Experiments in the county of Malmöhus in south-western Sweden. The soils are from four fields in these experiments, two crop rotations, and four PK levels. Before and after the pot trial, soil samples were extracted according to a sequential fractionation method developed from the ‘Hedley procedure’. During the pot trial there was a large decrease in the resin P fraction. There were also decreases in the bicarbonate-Pi, NaOH-Pi, acid P and residue P fractions, but an increase in the NaOH-Po fraction. Resin P and NaOH-Pi seemed to be the most important fractions for explaining the P uptake by plants.