Abstract
The agronomic performance of three phosphorus sources-ground rock phosphate (GRP), a mixture of ground rock phosphate and elemental sulphur (Rock-S) and single superphosphate (SS)-was examined using maize as a test crop. Although yields of the GRP treatment were initially poor compared with SS, the differences disappeared by the third year indicating that the P fertility level of Nigerian savanna soils can be improved by annual applications of ground rock phosphate. Acidulation of the rock phosphate with elemental sulphur resulted in both improved solubility and improved P utilization. There is need for more work in the use of the relatively cheap GRP as a basal dressing to increase soil nutrient reserves up to the point at which it would be economic to apply annual maintenance dressings of more expensive superphosphate.
