Some chemical characteristics of selected geological materials in Cameroon (Central Africa) and their potential use for crop production.

This study was carried out in order to characterize some selected local geological materials so as to prove their potential use for crop production. For this purpose, two types of volcanic breccias, volcanic ash and marl from West Cameroon region were selected for chemical characterization. These chemical analyses were done in order to determine total concentrations, extractible fractions, the readily available fractions and water-soluble fractions of nutrients. The results showed that all materials tested were alkaline to neutral (pH = 9.04 to 6.79), with significant difference (p < 0.05) in values from breccias 3 to volcanic ash. Concentrations of macronutrients (N, P, K, Mg, Ca, and C) and micronutrients (Cu, Zn, and Mn) and their availability were consistent with those reported in the literature. These materials contain acid–extractable fractions (5.3 to 61.3% of Ca; 0.6 to 10.5% of Mg; 8.5 to 49.95% of K; 2.59 to 95.6% of P and 0.07 to 3.7% of Na), readily available fractions complexed by ammonium acetate (5.14 to 32.76% of Ca; 0.06 to 9.09% of Mg; 7.52 to 35.9% of K; 0.84 to 3.33% of K and 0.00 to 0.04% of Na), and water soluble fractions (0.04 to 0.78% of Ca; 0.10 to 0.36% of Mg; 1.02 to 1.3% of K; 0.01 to 0.88% of Na and 0.09 to 1.04% of P) of some elements. K and Ca appear to be the most ready available elements in most samples (p < 0.05)) followed by Mg and Na (p < 0.05). Breccias gave the highest release of Ca, Mg, K, and Na, but a low release of P in water. Nutrients were less soluble in the volcanic ash. K appears to be the most water-soluble element in all the materials. The amounts of nutrients released during the kinetic study (50 to 91% during the first 30 minutes of shaking) were comparable and/or higher in some cases than those obtained in most agrogeological materials in the world. These materials, highly concentrated in macro and micronutrients required for plant growth and easily releasable, are likely to add nutrients to the soil. Keywords: Agrogeological materials, Cameroon, macronutrients, micronutrients, chemical extraction.International Journal of Biological and Chemical Sciences Vol. 2 (1) 2008 pp. 21-32