The role of living plant roots and cattle manure as a soil amendment in the alleviation of compacted coal mine soils

Abstract

In South Africa, most of the surface coal mines are situated on the Highveld of the Mpumalanga Province. The mining industry plays a vital role and contributes to the economy of the country. Very often the mining activities change the physical nature of the soil which results in soil compaction. In mine soils, compaction is of great importance in plant growth and the environment because its high levels may adversely result in the degradation of soil structure, reduced nutrient distribution and reduced root growth, which eventually decreases plant growth. To ensure a productive vegetation, compacted mine soils has to be ameliorated effectively. A combination of practices is suggested to alleviate soil compaction, but some of them are costly and not ecologically stable particularly the use of conventional methods. Therefore, the challenge is to use the potential practices to ameliorate compacted soils. The proposed investigations, which are envisaged to solve harmful effects of soil compaction on plant growth, include biological activities, achieved through appropriate application of cattle manure and planting of pasture species. A review on literature, some studies indicate that the application of organic manure amendments such as cattle manure may overcome the negative effects of compaction, due to the beneficial effects on soil physical, chemical and biological properties in the zone of incorporation. Other studies has shown that pastures are linked with improvements in soil structure, soil organic matter content, rooting depths, consequently, reductions in bulk density. The focus of this study were to monitor the root biomass of irrigated Tall Fescue (F. arundinacea cv Dovey) and dryland Smuts Fingergrass (D. eriantha cv Irene) on mine soils, and to describe soil bulk density and soil nutrient concentrations in such soils. This study were also determining the effects of incorporating cattle manure into compacted (mine soils) and non compacted (agricultural soils) and evaluating its effects on the seedling growth rate, dry matter and root biomass production of Tall Fescue and Smuts Fingergrass. In addition, the influence of different rates of cattle manure on soil bulk density and nutrient concentration in such compacted soil was also measured. These parameters are relevant to the sustainable rehabilitation of mine soils. Based on the results obtained in this study, it was concluded that the use of two grass species, Tall Fescue and Smuts Fingergrass, with vigorous root systems have extended their roots in compacted mine soil layers over two growing seasons. Other results have demonstrated that application of cattle manure revealed a significant decrease in soil bulk density of compacted mine soils planted to Tall Fescue and Smuts Fingergrass. The bulk density was at a minimum in the 80 tha-1 cattle manure-treated plots and followed by the 40 tha-1 cattle manure treatment, and the maximum bulk density was recorded for the control treatment (0 tha-1). The application of cattle manure resulted in a large input of nutrients to the soil as compared to untreated control and significantly increased Tall Fescue and Smuts Fingergrass growth and production. This research has illustrated that use of plant roots and cattle manure as soil organic amendments to reduce soil compaction may be environmentally and economically beneficial leading to a more sustainable agricultural system. Copyright