Water Relationships of Claypan and Constructed Soil Profiles

Abstract Claypan soils with poor physical properties are the only surface materials available to cover and reclaim much of the spoil left by strip mining for coal in east‐central Texas. We compared an undisturbed claypan soil profile of Axtell fsl fine montmorillonitic, thermic Udertic Paleustalfs) to four constructed soil profiles and evaluated them as cover soils for toxic minespoil. We compared profiles constructed from minespoil selected for low pyrite content alone (non‐topsoiled) against the same selected spoil covered by a mixture of Axtell soil material. The rainfall intake rate and physical properties of the materials controlled forage production by kleingrass ( Panicum coloratum L.). All of the constructed soils stored less water in the soil profile than the undisturbed claypan soil, and forage yield was reduced on them during drought. Infiltration rate during the first 2 cm of rainfall influenced forage yield more than final intake rate. Mulch application increased water storage and forage yield up to 15% on selected minespoil, but not on the mixed claypan soil profiles. Either selected minespoil or a mixture of Axtell soil may be used to cover toxic random soil with a nontoxic layer, but the Axtell mix had the least acid‐forming potential. Selected minespoil material was equal in value to a mixture of the 1.8 m claypan soil profile as a surface material for constructed minesoils.