Exchangeable aluminium and acidity in Acrisols and Ferralsols of the north-west highlands of Cameroon

Abstract

Diminishing crop yields in the Western Highlands of Cameroon is largely attributed to soil acidity. Soil characterization was carried out on six highly weathered soils developed from pyroxene-rich basalt in the North-West Region (NWR) of Cameroon to evaluate their use potential for agricultural production. These soils are acidic in nature, and have high exchangeable Al contents. Clay contents are high and CEC is low. The organic matter contents are moderately high and decrease with depth and act as sinks for exchangeable Al as indicated by the high correlation between them. The high amounts of sesquioxide coatings in the subsurface B horizons may be reducing the amount of extracted Al leading to low exchangeable Al in these horizons. Correlative statistical relationships were established among soil properties including clay percent, exchangeable Al, CEC, organic carbon content, pH-KCl and pH-water. Regression equations established between exchangeable Al and pH-H2O and exchangeable Al and pH-KCl were best described by quadratic models.Based on the correlation that exists between exchangeable Al and pH-KCl, these equations can be used to estimate the lime requirements of these soils after transformations based on the neutralization index proposed in this study. Regression relationships so established constitute useful predictive indices for estimating agronomic properties from existing physical and chemical data and soil survey reports. Grouping of soils with similar characteristics would produce correlative equations that give more reliable predictive results.