Liming of wetlands in the Roynelandsvatn catchment - Effects on soil chemistry and neutralisation properties in the soil profile

In 1990, wetlands in the Roynelandsvatn catchment in Southern Norway were limed with finely ground limestone powder at a rate of 20 t ha(-1) to remediate acid discharge. JORDFORSK has investigated changes in the chemical properties of soil over a three yea period in a selected limed fen. Calcium (Ca) contents above natural background levels were found in the uppermost 20 an of the peatsoil The major part of Ca introduced by liming in the uppermost 3 an of the peatsoil Remaining Ca from liming is roughly estimated to be 2,5-3 t ha(-1). similarly, pH of the uppermost an of the peatsoil of the limed far was around 7. Deeper peatsoils (> 29 an) had pH-values around 3.8-4.9. After liming the dominance of hydrogen (H)- and aluminium (Al) ions in the exchangeable cation pool was replaced by Ca in the uppermost an of the fensoil. In deeper peatlayers (> 20 cm) the exchangeable cations were still dominated by H+ and Al-ions. A smaller part of organically bound Al in the lime-influenced mire topsoil than in other peatsoil may indicate that Al has changed from an organically bound to a mineral (amorphous) phase. The liming has changed chemical properties of the uppermost pit of the soil. This will counteract acidic and Al-rich input The results underline the origin of acid-neutralising effects and stress the importance of hydrology and patterns of water now in the surface layers of mires.