Use of montmorillonite-enriched sandstone to remediate a sandy mined soil

Abstract

Man-made soils (technosols) could be a practical alternative when the availability of suitable natural topsoil is limited in surface mine areas for reclamation. Screening potential topsoils is a necessary step to determine the suitability of materials for revegetation. This study aimed to obtain insights into the growth of alfalfa (Medicago sativa L.) on homogeneous and layered initial soils prepared with local natural materials (sandy soil and montmorillonite-enriched sandstone), before screening the optimal topsoil for alfalfa growth. Ten technosols were assessed in a growth study over 5 months by using the biomass production and root system as performance indicators. The shoot and root biomass production were highest in the treatment with a 20 cm montmorillonite-enriched sandstone layer at a depth of 20–40 cm, where the biomass production rate was approximately twice that in sandy soil. The root distribution according to the depth was more even in a homogeneous mixture of sandy soil combined with montmorillonite-enriched sandstone and the treatment with a 20 cm montmorillonite-enriched sandstone layer at a depth of 20–40 cm compared with the other eight options, possibly due to the higher water-holding capacity of the montmorillonite-enriched sandstone. The optimal technosol was determined as a 20 cm montmorillonite-enriched sandstone layer at a depth of 20–40 cm in a sandy matrix. The results of this study using locally sourced components for preparing topsoil could facilitate the development of strategies for mine reclamation.