REVEGETATION OF WASTE FLY ASH LAGOONS II. SEEDLING TRANSPLANTS AND PLANT NUTRITION

As an alternative or in addition to direct seeding, container-grown transplants provide a means of economically and rapidly revegetating waste fly ash lagoons through the expeditious establishment of vegetation islands. Survival and growth ofEnchylaena tomentosaandNitraria billardiereitransplants were largely dependent on the size of the root volume at transplanting. Growth response of both species in fly ash increased significantly as transplant container size increased from 110 ml to 800 ml. Fly ash incorporated into the potting mix during the containerised stage of growth generally reduced plant growth and survival following eventual transplantation. Gradual hardening ofEnchylaena tomentosaseedlings to increasing concentrations of fly ash in the potting mix (25 to 50 to 75% fly ash), however, improved immediate survival following transplantation, into pure ash. Nitrogen deficiency in Port Augusta fly ash was a major nutritional limitation to growth of these two species. Growth and dry matter production responded optimally to application of N fertiliser (NH₄NO₃) at 100–150 kg N ha⁻¹. Although bicarbonate-extractable P levels in fly ash were high (over 250 mg kg⁻¹), a response ofEnchylaena tomentosato supplementary P application [Ca(H₂PO₄)₂.H₂O] at 100–200 kg P ha⁻¹was observed.N. billardiereidid not respond to supplementary P, and it was suggested that fly ash P may be selectively available to plants on a species dependent basis. No growth responses to K application (KCl) at rates of up to 400 kg K ha⁻¹were found.     

SOLID WASTE COLLECTION SYSTEMS IN DEVELOPING URBAN AREAS OF SOUTH AFRICA: AN OVERVIEW AND CASE STUDY

Experience with appropriate collection systems for urban and peri-urban areas of developing countries is accumulating. Nonetheless, the primary lesson learned from studying such systems is that collection systems must be designed to accommodate the particular conditions of the community. This paper reflects on international experience with such collection systems and examines their relevance to South Africa. A case study is presented of designing a solid waste collection system for the Winterveld, Bophuthatswana, including a community survey, a waste composition study, and exploration of resource recovery options. Detailed data from the case study show that, even within one country, solid waste collection systems are not automatically transferable from one community to another. Particular recommendations for the South African situation are given.