Morphological, mineralogical and geochemical features of topomorphic vertisols used for sorghum production in North Cameroon

Abstract

In the present study, two topomorphic vertisols profiles used for sorghum productionwere described and characterized. After macroscopic characterization, physicochemical,mineralogical and geochemical analyses were made. Physicochemical analyses were madeby standard methods while mineralogy was determined on clay fraction (˂2µm) by X-raydiffraction coupled to Fourier transform infrared spectroscopy. Geochemical analysis wasdetermined on 180µm fraction by inductively coupled plasma- Atomic EmissionSpectroscopy (ICP-AES) and mass spectrometry (ICP-MS). Results revealed that studiedvertisols were average deep, less differentiated with desiccations cracks and gilgai microrelief. The angular blocky structure and clayey texture were observed. They were alkaline(7.3 ≤ pHwater ≤ 8.4) and recorded a low to moderate organic matter and nitrogen contents.Cation exchange capacity was high reaching 52.24 meq 100g-1 and exchangeable cationswere moderates with Ca2+ (3.69- 29.6 meq 100g-1) the most represented cation. Vertisolswere made of smectites associated to kaolinite and a lesser content of quartz. Illites andcalcite were also identified in some horizons. On the geochemical point of view, Si02(55.87- 83.64%), Al2O3 (6.08-20.25%), Fe2O3 (2.09-6.39%) and K2O (1.43-2.24 %) werethe dominant oxides. Traces elements were represented essentially by Ba (518-1202 mgkg-1), Zr (334-685 mg kg-1) and Sr (71-190 mg kg-1). The overall features are suitable todry season sorghum production. The amount of smectites seemed to be an importantfactor affecting their water holding capacity on which dry season sorghum productiondepends. Improved cropping systems have to be developed to sustain productivity invertisols with low smectites and where annual rainfall is lesser.