Influence of Soil Fertility on Botanical Composition of Rehabilitated Pastures in South Africa

Abstract

Abstract. Soil conditions created during the rehabilitation process of strip-mined areas differ from the original in respect of depth, density, drainage, organic material content, fertility and microbial activity. This paper reports on the influence of soil fertility on the botanical composition of pasture established on such areas. The study was conducted on a site with grassland capability classification, making it suitable for utilization as reclaimed rangeland QI as planted pasture. The ultimate land use would be determined by economic and ecological considerations. Over an experimental period of five years (1987)(1988)(1989)(1990)(1991)(1992) it was found that of the seeded species the annual Eragrostjs ill and weakly perennial Ch)orjs gayana disappeared completely, irrespective of the level of fertility, whereas the perennial Djgjtaria eriantha persisted as the dominant species irrespective of soil acidity, phosphorus or potassium status. In contrast, Medjcago satjya was extremely sensitive to low pH, phosphorus or potassium and was completely eliminated under such conditions. It was particularly noteworthy that volunteer species such as Cynodon dacty)on and Eragrostis curvula increased under low phosphorus/low nitrogen treatments and low pH conditions respectively. These results hold important implications for policy decisions concerning sustained levels of fertilization, the composition of seeding mixtures and the consideration of pasture reinforcement at a later stage where the restoration of a greater diversity typical of a rangeland situation may be an objective.