Landscape-scale spatial variability of kaolinite-gibbsite ratio in tropical soils detected by diffuse reflectance spectroscopy

•The mapping of minerals for large areas by conventional techniques is costly.•The diffuse reflectance spectroscopy is an efficient indirect technique.•Spectroscopy has been widely used for quantification of soil minerals.•The technique allowed the quantification of the minerals kaolinite and gibbsite.•Maps of the minerals provide information to define management zones.