Earthworms and Structure Rehabilitation in Subsoils and in Topsoils Affected by Opencast Mining for Coal

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Abstract
Because soil structure seems to benefit from the period under grass in a normal rotation, it is widely assumed that grass roots are primarily responsible (Strutt, 1970). Due credit is also given to efficient drainage, adequate inputs of organic matter, lime and microbial activity. However, it is not clear whether the earthworm is a passive exploiter or a causal agent of structure improvement. When the pressures of production end up in severe soil structure deterioration, or when massive soil disturbance and stockpiling ends up in soils restored with little residual structure, experimental evidence suggests that the role of the earthworm is crucial. Evidence will be presented to show how earthworms, in association with all the other factors normally held to be responsible, initiate the development of water-stable, soil granulation. However, evidence will also be presented which shows how certain features of modern agriculture are, to some extent at least, antagonistic to earthworms. In utilizing degraded land, it may be necessary to farm initially for the benefit of the earthworm rather than for yield. This approach must be maintained despite the fact that, in the early stages, it may result in a phase of greater waterlogging and susceptibility to poaching.