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Abstract
The aim of the paper is to Identify major soil plant fertility constraints for 15 soil profiles from the Lusikisiki area of the Eastern Cape Province of South Africa. Phosphorus levels were very low, with 87% of the A horizons having a Bray-1 extractable P content of < 3 mg kg−1. Most soils (80%) will require K fertilization for adequate crop yields. The Ca status is adequate in 73% of the A horizons, albeit at the lower end of the recommended scale. Extractable Mg contents were adequate in most soils, an unexpected finding for this highly leached environment. The exchangeable Ca: Mg ratio is low and only four profiles have values of > 2 in the A horizons. The lowest ratio was 0.25. The organic carbon content is high for South African conditions, averaging 3.63% in the A horizons. The Sum of base cations as well as the CEC are more closely related to soil organic matter than to exchange sites of the clay minerals and an average of 70% of the CEC in the A horizons is associated with organic carbon. The decomposition of small amounts of organic matter will therefore lead to a significant reduction in the CEC.
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