PHOSPHORUS SPECIES IN A FIELD RECLAMATION EXPERIMENT OF A COAL-MINING DUMP

In the autumn of 1990 soil samples from 15 different plots of a field experiment cultivation area on a former coal mining waste heap were taken to characterize phosphorous species. In the upper 10 cm of the colliery spoil soil up to 30 % of total phosphorous is bound in the soil organic matter. The phosphate fixed in Ca phosphates is in nearly all cases below 1 % of total P. Up to 63 % of total P are accumulated as Fe and Al phosphates. The amount of water soluble phosphates is strongly reduced by the amount of hydrous iron oxides. The small amounts of lactate leachable phosphate show that P is a strong limiting factor in plant nutrition on soils of coal mining dumps. Besides the investigations showed a rapid acidification of the coal mining waste substrate which results from pyrite oxidation. Some plots of the field experiment area are acidified to pH (CaCl2) 2.6, this is in some cases a decreasing by 4.6 pH units which is a remarkable change within 3 years.