Fertilization effects on surface peat of pine bogs

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Abstract
Bulk densities and chemical properties of surface peat (0–60 cm) of three ombrotrophic pine bogs were measured before and three growing seasons after fertilization. One site was located in each of the countries Norway, Sweden and Finland. Bulk density of peat ranged from 56 in Norway, 78 in Sweden to 130 g dm‐3 in Finland. Bulk density seems to vary along a sub‐coastal to sub‐continental gradient for the bog type. When compared to the biological demands of the tree stands, the surface peat stores of extractable K, P and B were low before fertilization. Depletion from the peat on fertilized plots (uptake and/or leaching) were rather high for K, B, Mn and Zn. Especially the sodium borate (borax fertilizer) was susceptible to leaching. Only minor changes occurred in’ pH and cation exchange capacity after fertilization, whereas base saturation was raised, especially in the upper layer (0–10 cm). A high proportion of total K, Ca, Mg, Mn and Zn were on exchangeable sites (63–92%), while P, S. B and Fe were mainly fixed (72–95%). Estimated net carbon loss from the peat at drainage was 100 g Cm‐2 year‐1, while at additional fertilization the loss was only 6 g.