Effect of wood ash on soil chemistry and the nutritional state of pine stand on a Podzol in northern Germany : Forest Ecosystem Restoration

2000

S. 229-234

1 Abb., 3 Tab., 10 Lit.

Unselbständiges Werk

200072964

Addition of wood ash on acid soils may have ameliorative as well as negative effects on soil chemistry and nutritional state of forests. The objective was to quantify these effects for a pine stand in northern Germany. A field experiment was carried out at a fifty-year old pine stand on a sandy Podzol at Fuhrberg (Lüneburger Heide) which included superficial additions of wood ash (nil, 2.4 and 4.8 t ha®Ü). Soil solution chemistry was investigated monthly at different depths. Prior and after the experiment (18 months later), exchangeable cations and contents of heavy metals were determined at different depths and needle contents were studied. Four months after addition of 2.4 and 4.8 t ha®Ü wood ash, maximum concentrations of Ca and K were found in the soil solution. Catio exchange reactions resulted in a slight increase in Mg concentrations but not in Al concentrations. pH values dropped temporarily by 0.2 (2.4 t ha®Ü) and 0.6 (4.8 t ha®Ü) units at 10 cm. Nitrate concentrations increased at all depths. Concentrations of Pb and Cr did not change significantly (p < 0.05) after ash addition, but concentrations of Cd and Zn increased significantly at some depths. However, maximum concentrations of nitrate and heavy metals were well below the German legal limits for drinking water. Eighteen months after addition of 2.4 or 4. 8 t ash ha®Ü, cation exchange capacities (CEC) and base saturation of the upper 6 cm of the organic layer increased significantly. Contents of Cu increased by a factor of two (2.4 t ha®Ü) or 5 (4.8 t ha®Ü) in the upper 4 cm of the organic layer. Increases of the contents of Cr and Zn were less, but significant. In the upper 10 cm of the mineral soil, EDTA extractable Zn and Cd increased by a factor of 1.5 and 3.5 at additions of 4.8 t ha®Ü. K contents of the 1-year old pine needles increased significantly from 5.6 to 5.8 (2.4 t ha®Ü) and 5.9 g kg®Ü (4.8 t ha®Ü). The results suggest that ash from untreated wood (using modest additions) may be recommended for amelioration of forest soils if no adverse effects occur in the medium term.