Diagnostic of Mineral Deficiencies and Interactions in Upland Rice Cropping Across Different Agroecologies of West Africa

Abstract

Haphazardly fertilization can impaired rice production inducing yield declining in continuous cropping even with high input management. Ecological difference can account for such weakness of upland rice agrosystems. Thus, omission multi-locations trial was conducted in humid forest and guinea savanna of Cote d’Ivoire as well as the sudan savanna of South Mali and a derived savanna of South Benin. A complete fertilizer treatment (Fc) was composed of N (80 k gha⁻1), P (100 k gha⁻¹), K (50 k gha⁻¹), Ca (50 k gha⁻¹), Mg (50 k gha⁻¹) and Zn (50 k gha⁻¹) while six other treatments were defined by excluding of a specific nutrient (Fc-N, Fc-P, Fc-K, Fc-Ca, Fc-Mg and Fc-Zn) and not fertilized plot was the control. Soil test, rice grain yield and Chaminade index were used for assessing soil nutrient deficiency. Soil K deficiency was often observed according to soil test unless in the subsoil (20–40 cm) coupled with unbalance ratio of cations. Slight to moderate deficiencies of N (savanna ecologies) and P (forest) were observed by Chaminade method and a latitudinal gradient of soil nutrient deficiency was emphasized. Basal fertilizer requirement was identified as NPKMg, NPKZn, NK and NPK in the forest, derived savanna, guinea savanna and sudan savanna respectively with specific composition for each cropping season. Nevertheless, declining yield in continuous cropping was characterizing upland agrosystems indifferently to ecology and fertilizer composition.