Abstract

MADEIRA, Manuel  and  RICARDO, Rui Pinto. Exchangeable complex and taxonomy and management of Ferrallitic Soils from Angola. Rev. de Ciências Agrárias [online]. 2015, vol.38, n.3, pp.394-410. ISSN 0871-018X.

The cation exchange capacity, sum of exchangeable bases, and saturation base degree of Ferralitic soils from the Republic of Angola, determined by the Mehlich and ammonium acetate methods, were compared to update their taxonomy; also, the exchangeable acidity was determined for deeper insight in their classification. Fourty eight representative pedons of subordens of those soils (Tipoferralic, Weakly Ferralic and Psamoferralic) were analysed. Values of sum bases and exchangeable Ca²⁺ and Mg²⁺ by the two methods were strongly correlated; cation exchange capacity, base saturation degree and exchangeable K⁺ showed weaker and variable correlations, according to soil type. Exchangeable acidity largely corresponded to Al³⁺, but its content was mostly less than one cmol_c kg^-1; its percentage regarding the effective cation exchange capacity was mostly higher than 60%. Study soils show in overall subsurface horizons with the characteristics of a ferralic horizon; therefore, they are mostly Ferralsols, which can be separated at first level in geric, vetic e haplic Ferralsols, according to the effective cation exchange capacity value; also, at second level they are largely dystric and, in great proportion, alumic. The weakness of study soils regarding the low nutrient retention capacity can be alleviated by organic matter additions and liming.

Keywords : ammonium acetate method; angola; cation exchange capacity; ferralic horizon; Mehlich method.

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