EARTHWORM OCCURRENCE IN AGRICULTURAL RECLAMATION AREAS OF THE LOWER RHINE BASIN

Until late 1990 the lignite mining industry utilized agricultural land covering 16,051 hectares in the Lower Rhine Basin, 6,926 hectares of which was meanwhile reclaimed for its former use. The yield potential of these reclaimed soils depends to a very large extent on their water holding capacity and rootability. Since the soil structure is completely destroyed during material removal and compacted as a result of the construction process, particular importance is attached to the activities of earthworms in these young soils because these animals can reduce the effects of such damage. In the fall of 1989 and the spring of 1990 different sites (36) were selected to examine the influence of the reclamation year, method and quality, and of cultivation on the abundance of earthworms. The animals were expelled by means of diluted formalin solution. Species and genus of these animals were determined. The population of earthworms increases with area age. It is smaller on young and middle-aged flushed areas than on those of the same age, but constructed according to the dry dumping method. The plots cultivated without ploughing for three years had a considerably greater earthworm population compared to other areas. It was not possible to demonstrate any influence of the reclamation qualify on the abundance of earthworms; the addition of organic substances, however, had a positive effect. Stable manure (turkey hen manure) was more efficient than green manure and straw chaff. Thus, cultivation promoting earthworm development can also produce a relatively high earthworm population density in reclaimed soils which in turn is of major importance for biogenic loosening-up (stabilization of the soil structure).