Geostatistical Variability of Nitrogen Content, pH, and Carbon Stock in the Soils of the Sudan-Guinea and Guinea Zones of Benin: A Kriging Approach

Abstract

Soil fertility is a determining factor for agricultural productivity and food security. This study aims to map the spatial variability of soil fertility parameters (nitrogen, pH, and carbon) in the Sudan-Guinea and Guinea zones of Benin using geostatistical approaches. To achieve this objective, fifty-two (52) soil samples were collected using a stratified random sampling design and analyzed at the Soil, Water and Environmental Science Laboratory (LSSEE) of the Agricultural Research Center based in Agonkanmey, Abomey-Calavi. Total nitrogen, organic carbon content, and water pH were determined using conventional methods. Four kriging methods (simple, ordinary, universal, and indicator) were compared after fitting three variogram models (spherical, Gaussian, and exponential). The results reveal that the spherical model provided the best fit to the data for nitrogen, pH, and carbon. Indicator kriging proved optimal for nitrogen (RMSE = 0.47), simple kriging for pH (RMSE = 0.40), and ordinary kriging for carbon (RMSE = 0.41). Spatial analysis indicates low nitrogen content (0.08% ± 0.03%), slightly acidic pH (6.63 ± 0.22), and carbon content (0.79% ± 0.17%). The carbon stock was estimated at 1.62 t∙C∙ha − 1 , revealing a moderate sequestration potential. These results provide a scientific basis for differentiated soil fertility management in these agro-ecological zones.