Compaction implies an increase in soil bulk density and associated with this are increases in soil strength, and decreases in air permeability and hydraulic conductivity. This paper considers the mechanics of compaction and then proceeds to consider the effects of that compaction on the biotic activity in the soil. The elongation of roots through soil is considered in detail and we draw attention to controversy in the literature and the current debate on the appropriateness of models based on the traditional Lockhart approach to root elongation. A model of root elongation which can be used in practice is also discussed. Soil fauna considered include earthworms, which can physically move soil and micro fauna which cannot. Consideration of microbial activity and biological interactions shows that the effect of compaction on a given soil depends on its management history. Further research is required to develop systems of agriculture which are sustainable and ecologically sound, because the effects of tillage and compaction on biological processes in the soil are only partly understood.
Whalley, W.R.; Dumitru, E.; Dexter, A.R. Biological effects of soil compaction. Soil and Tillage Research (1995) 35 (1-2) 53-68. [DOI: 10.1016/0167-1987(95)00473-6]