Comparison of rehabilitation methods on mechanically reconstructed soils following strip coal mining activities: effects on grass properties

Abstract

Opencast coal mining has devastated the grassland biomes in the Mpumalanga Province of South Africa. A rain-fed rehabilitation trial on mechanically reconstructed soil, following strip coal mining, was conducted to demonstrate that the post-mining landscape can be returned to sustainable land use. Information is lacking on the interactive effects of rainfall, soil and vegetation properties as a function of rehabilitation procedures. Hence, various rehabilitation treatments and topsoils were evaluated over three seasons, using a grass mixture comprising of annual and perennial species. Trial measurements included soil properties, as well as the growth and chemical composition of the grass stand. Statistical significance was observed for most measurements as a result of the treatments. A large variation in grass nutrient properties was observed as a result of treatment effects. A decreasing trend in canopy nutrient content over time was found. This study of soil-plant nutrient relationships revealed that low canopy nutrient contents were a consequence of insufficient soil nutrient levels. The monitoring of soil fertility and plant properties should be a prerequisite in any rehabilitation study, and soil fertility should be maintained to support sustainable plant growth. Trials on different soils and in different rainfall regions, with increased topsoil thickness, should be considered.