Why can smoothing mine spoil banks make plant growth more difficult?

Smoothing mine spoil banks can hinder plant growth because the process often leads to excessive compaction of the spoil material. While smoothing is frequently required by legislation to improve the topography of these sites, the resulting density makes the ground less suitable for vegetation to take root and thrive.1

In their natural state, spoil banks created by surface mining are typically loose and porous. When this material is mechanically leveled or graded, the loss of that porosity restricts the conditions necessary for healthy plant development. Consequently, because of these physical challenges and the often raw, infertile nature of the material, reclamation efforts are generally limited to reforestation or the development of grazing and recreational areas, rather than the cultivation of crops.1