Distribution of free and total aluminium in some cocoa-growing soils of Ghana

Abstract

The Western Region of Ghana is currently carrying the bulk of Ghana's cocoa, and so it is important to investigate the amounts and distribution of total and free Al oxides in some cocoa-growing soils from the region. Six soil series belonging to one major compound association of soils occurring in a toposequence, the Yakasi-Elubo/Oda Compound Association, was used. Soil profile pits of 1 m2 and to different depths were prepared for each soil series, and soil sampled from different genetic horizons of the profiles and analysed for total and free Al oxide contents and other soil properties. The amount of total and free Al oxide in the profiles increased with depth. The mean values for total and free Al oxides for the surface soils (A-horizons) were 505.7 and 194.3 mmoles Al2O3/kg soil, respectively, and those for the B-horizons were 648.9 and 289.5 mmoles Al2O3/kg soil, respectively. The pattern of distribution of total and free Al oxides were similar and closely related to the distribution of clay. Except in the lowland soil where pH was higher in the A-horizon, pH generally decreased with depth where there was maximum accumulation of Al oxides. The upland soils contained higher amounts of Al than the lowland soils of the catena. The higher amounts of Al in the soils may limit cocoa cultivation.



Ghana Jnl.agric. Sci Vol.32(1), 1999: 101-108