Promoting Uses of Indigenous Phosphate Rock for Soil Fertility Recapitalisation in the Sahel: State of the Knowledge on the Review of the Rock Phosphates of Burkina Faso

Abstract

The widespread phosphorus deficiency in tropical soils constitutes one of the main factors limiting crop production in sub-Saharan Africa. This review documents the experiences in the use of Burkina rock phosphate in the recapitalisation of soil P fertility in order to increase agricultural production. The research found that the rates of rock phosphate recommended for major crops were (i) 400 kg ha^–1 in first year and 100 kg ha^–1 year^–1 for the following years or 200 kg ha^–1 every year for sorghum, maize, cotton, peanut and cowpea; (ii) for the pluvial rice it is recommended to apply 500 kg ha^–1 in first year and 200 kg ha^–1 year^–1 for the following years; and (iii) 600 kg ha^–1 in first year and 300 kg ha^–1 year^–1 the following years for the irrigated rice. The research developed a formula for partially acidulated rock phosphate as 4.22 N – 24.55 P₂O₅ – 6.26 S – 25.52 CaO – 0.16 MgO. This product is practically equivalent to TSP in terms of the production of cereals and is better in terms of increasing the nutrient content in soil; it is also economically profitable. Another finding was that phosphate rock solubility could be improved by adding 80 kg of PR per tonne of organic residue at the beginning of the composting of organic residues. Mixed formulas combining 75% rock phosphate to 25% TSP or 50% rock phosphate + 50% TSP for the rotation with cowpea increased sorghum production. Thus, rock phosphate can be effective in the managing soil degradation, in the recuperation of degraded soils, and in the stabilisation of crop production for a lasting agriculture.