Nitrogen (N) fertilizer is commonly used to improve soil fertility and maize production in Cameroon, but high cost and potential environmental effects have necessitated site-specific N fertilization regimes that are adapted to particular soil and crop types. A field experiment was conducted with five N application rates (control–0, 50, 100, 150, and 200 kg N ha−1) to determine optimum rate for best maize yield with limited effect on soil acidification. The soil residual N ranged from 0.18 to 0.36% across N application rates and increased at higher application rates with the highest in 150 and 200 kg N ha−1. Soil C/N ratio ranged from 7.5 to 15.5 across N rates with the highest in control, which decreased at higher N application rates. Soil pH ranged from 4.7 to 5.4 across N rates, with the lowest in 200 kg N ha−1 rate. Maize grain yield and cob length ranged from 7.1 to 10.3 t ha−1 and from 14.5 to 18 cm across N rates, respectively, with the highest in 150 and 200 kg N ha−1. Maize 1000-grain weight ranged from 380 to 560 g across N application rates with the highest in 100, 150, and 200 kg N ha−1. Significant negative correlations occurred between soil pH and maize yield or 1000-grain weight. Maize N use efficiency decreased sharply at higher N application rates, as demonstrated by a strong negative correlation between the N-Partial Factor Productivity and total soil N. Overall, the lower soil pH at higher N application rates highlights the potential for deleterious effects of N fertilizer inputs on arable soils, which may eventually affect crop productivity, thereby suggesting lower N fertilization regimes between 50 and 100 kg N ha−1 as the optimum for maize production on the volcanic soils of Buea.

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