Retention of Ca and Mg in the forest floor of a spruce stand after application of various liming materials

Abstract

In a forest stand lime is commonly applied to the forest floor to neutralize acidity and to improve buffering capacity of soil by the addition of carbonate and other anions of weak acids. This is expected to cause major chemical changes in the forest floor. In this study, different liming materials, equivalent to 60 kmol c Ca 2++Mg 2+ ha −1, were applied to the forest floor of a spruce stand. The limes were dolomite, mixtures of dolomite and calcite or chalk, and silicate industrial slag lime (‘Hüttenkalk’) of varying particle size combinations. Two years after lime application, salt extractable Ca 2+ and Mg 2+ was measured in the forest floor using a sequential percolation method. This method allowed the assessment of Ca 2++Mg 2+ present on exchange sites by distinguishing between the amounts released upon dissolution of residual, undissolved liming material. In all cases there were major changes in exchangeable content of Ca 2+ and Mg 2+ in the L+F layer, whereas changes in the H layer were small. Differences in the effects of liming materials on the litter layer were attributed to their texture, the contents of Ca 2+ and Mg 2+ and the associated anion (carbonate or silicate). High content of exchangeable Ca 2+ and Mg 2+ was observed in the forest floor when liming materials were of high Ca and Mg content and of fine texture. The sum of exchangeable Ca 2++Mg 2+ in the forest floor increased from 7 kmol c ha −1 (control) to 17–26 kmol c ha −1 after liming and accounted for 15.5–31.5% of Ca+Mg applied. This increase in exchangeable Ca 2+ and Mg 2+ of L+F layer indicates large amounts of lime may be required to ameliorate mineral soil at depth, and that the content of these cations will partly determine future lime requirement of the spruce stands.