Soil rating for crop production in the savanna belt of south-western Nigeria

Abstract

A method for grouping soils for specific purposes is presented using the example of maize in the savanna ecological zone of south-western Nigeria. The technique involves two important stages. The first is the identification of the crucial soil properties influencing maize production in the study area while the second is the actual rating of the soils based on the relevant soil properties identified. Using an index of soil variable contribution to the growth and yield of maize in the area, only two soil properties, the organic matter and the available moisture contents of the soils, contribute significantly (58·4% and 13·1%, respectively) to the growth and yield of the crop, out of the twenty soil parameters analysed. With respect to the second stage, six soil productivity classes ranging from A (Excellent) to E (Poor) were arrived at as far as maize production in the area is concerned. The assignment of scores to the two soil properties used in rating the soils was based on their relative contribution to the growth and yield of the crop. However, the results of the application to, and comparison of the rating scheme with, 29 local soil series previously assessed for rainfed maize production by Murdoch et al. (1976), largely indicate that, after carrying out the special purpose soil classification, there is still the need to engage in capability assessments of the land using other environmental parameters apart from the soil attributes.