Buffering of Peat and Peaty Soils: Evaluation Based on the Artificial Acidification of Peat Lysimeters

Abstract

Sphagnum peat, ligneous sedge peat and ash fertilized (101 ash ha−1 in 1937) Sphagnum peat profiles were irrigated over a 16-month period in the laboratory with acidified (H2SO4) water at pH 4, 3 and 2, using deionized water as control. Total sulphur (H+) deposition during the study period was 0.8 gSm−2 (0.051 eqH+m−2) at pH 4, 10.6 gSm−2 (0.663 eq H+m−2) at pH 3, and 115.7 g Sm−2 (7.233 eq H+ m−2) at pH 2. Outflow of elements was measured after each irrigation, and the peat profiles were analysed at the end of the experiment. Irrigation at pH 4 and pH 3 did not considerably change either the outflow of elements or peat quality compared to the controls. In the outflow from the Sphagnum and ligneous sedge peat profiles at pH 2 and pH 3 sulphate was the dominating anion, thus superceding the role of organic anions. From the ash fertilized profiles sulphate outflow was lowered owing to the probable immobilization of sulphur as calcium sulphate. It was concluded that further acidification of naturally acid peat soils at realistic acid loads is improbable. However, sulphur inputs might be effectively retained in anaerobic peat layers and, when oxidized to sulphate, take over the role of organic anions with a resulting increased strong acid input into watersheds.