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Published online by Cambridge University Press: 27 March 2009
The residual effects of sulphur-coated urea (SCU) fertilizers were evaluated by measuring the pH and mineral-N in the soil profile after 2 years of application of these fertilizers to soils in the various ecological zones of the savannah of Nigeria. Changes of 0·2–0·3 pH units relative to the control (without applied N) were detected on the sandier soils at Kadawa and Mokwa but not on the heavier Samaru soils. There was little or no difference among the sulphur-coated urea and calcium ammonium nitrate in their acidification effects. Also residual nitrogen levels were low in plots that received SCU but did not differ significantly from those of calcium ammonium nitrate.