Effect of Diamou Lime, Gypsum, and Tilemsi Phosphate Rock on Acid Soils of the Sudano-Sahelian Region of Mali

Abstract

Continuous cropping, use of chemical fertilizers, and lack of sound soil management practices on poorly buffered kaolinitic Alfisols of the Sahel have accelerated soil acidity and reduced exchangeable Ca and crop yield. This study was conducted at the Cinzana Experiment Station in Mali, to determine the relative importance of Ca and P for millet grown on Plinthustalf sandy and Haplustet clayey soils for three years. The soils selected had very low to medium Bray P1 and extractable Ca concentrations. Three local sources of Ca and one source of P, Diamou lime, gypsum, and Tilemsi phosphate rock (TPR) were surface applied at lime application(LA) of 0, 0.5, 1.0, and 2.0 CaCO3equivalent. Among the three Ca sources, Diamou lime increased pH and exchangeable Ca concentration of surface soil, TPR increased the Ca concentration in the surface soil, and gypsum increased the Ca concentration of both surface and subsurface soil, but like TPR had no effect on soil surface or subsurface pH. The degree of millet yield response to Ca source varied with soil and year. No response to Ca was observed in a low rainfall year, but a positive response to TPR occurred in all three years, regardless of rainfall. For the soils studied, TPR can be considered a good local source of Ca and P, with potential to reduce Al toxicity and/or Ca deficiency. In general, application of P was more critical than Ca for millet growth in these soils.