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Soil fertility constraints to sustainable crop production in the Sudano-Sahelian zone: case study on phosphorus and efficient use of indigenous phosphates rock |
Cahiers Agricultures. Volume 7, Number 5, 365, Octobre-Novembre 1998, DOSSIER : Fertilité des sols et environnement : quelques outils, indicateurs et approches récentes - II
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 Résumé
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Author(s) : André Bationo, Saidou Koala, Elias Ayuk |
Summary : Low erratic rainfall, high soil and air temperatures, soils with poor natural fertility, surface crusting and low water-holding capacity, are the main characteristics of the West African semiarid tropics. Present farming systems are unsustainable, relatively unproductive and detrimental to the environment. Plant nutrient balances for many cropping systems are negative, indicating that farmers are mining their soils. Studies have shown that it is often poor plant-nutrient supplies that limit land productivity in the Sahel rather than rainfall.
Phosphorus is one of the major constraints to crop production in West Africa. Some phosphate rocks indigenous to regions such as Tilemsi (Mali) and Tahoua (Niger) are suitable for direct application. Partial acidulation is one way of increasing the agronomic effectiveness of local phosphate rock. Rotations of cereals with legumes, application of organic amendments (e.g. crop residue) and P fertilizer with ridging can substantially increase P efficiency. In on-farm trials carried out in Mali, net production gains obtained after the application of Tilemsi phosphate rock were almost as good as after application of imported water-soluble P fertilizers. In Niger, once soil fertility was restored subsequent to the application of Tahoua phosphate rock, an additional pocket application of 3 kg P/ha of simple superphosphate gave higher benefits than conventional applications of 13 kg P/ha superphosphate. |
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