Sukulu phosphates: Agronomic studies
Extracts from - and links to - agronomic studies of Sukulu phosphate rock and derived fertilizers.
The ‘ore’ mined at Sukulu between 1962 and 1978 consists of residual soil, the weathering products of the Sukulu carbonatite with an average grade of 12.8% P2O5. Tororo Industrial Chemicals and Fertilizer Ltd(TICAF) started out by mining the residual soils of the North Valley, which contain approximately 32% apatite, 57% magnetite and goethite, as well as 0.25% pyrochlore. The apatite from the Sukulu soils was won through grinding and magnetic separation, followed by flotation. The apatite concentrate (40-42% P2O5) was acidulated with sulphuric acid and converted into single superphosphate SSP. TICAF produced approximately 160,000 tonnes of apatite concentrate (40-42% P2O5) from 2.16 million tonnes of ore (recovery was 7.4%). In 1969, TICAF produced 13,800 tonnes of apatite concentrate and 22,390 tonnes of single superphosphate (1.62t SSP/tonne of concentrate).
The phosphate resources of Sukulu have been investigated intensively. A comprehensive economic and engineering study was carried out by Bearden-Potter Corporation of Florida (financed by the World Bank) in the early 1980s (Bearden-Potter Co. 1982). However, the 230-million tonne Sukulu phosphate deposit has yet to be developed for a number of reasons, one being the high capital investment required for the production of soluble P-fertilizers (US $121 million) (Annual Mining Review 1988). In addition, the processing techniques proposed by Bearden-Potter Co. are technically sophisticated and capital intensive.
Various researchers have tested Sukulu PR on its agronomic performance, including Zake and co-workers (Zake et al. 1988; Nkwiine et al. ) and Butegwa et al. (1996a, b) and IFDC Owens 1988. Both research groups showed that Sukulu PR used as direct application P-fertilizer was ineffective on acid soils. Better performance could be achieved by combined application with organic matter and 25-75 kg sulphur per hectare (Zake 1988). The use of partially acidulated phosphate rock (PAPR) manufactured from Sukulu PR had a lower agronomic effectiveness than Sukulu PR compacted with TSP at a total P ratio of 50:50 (Butegwa et al. 1996a). The effectiveness of partially acidulated phosphate rock (PAPR) was low on soils with high fixing capacities (Butegwa et al. 1996b).
