Modelling soil properties from horizon depth functions and terrain attributes: An example with cation exchange capacity

Abstract

The objective of this study was to, through the distribution of some soil properties, modelcation exchange capacity (CEC) in soils formed on gently undulating coastal plain sands ofsoutheastern Nigeria using genetic horizon functions and terrain attributes. A total of 19profile pits were prepared, described and 104 genetic horizons were identified and sampled,processed and analysed in the laboratory. Data were generated on the soil characteristics,including particle size fractions, hydraulic conductivity, bulk density, organic carbon, pH andelectrical conductivity. Terrain attributes that were generated from digital elevation modelinclude aspect, compound topographic index (CTI), Flow direction, curvatures, slope andstream power index (SPI). Data generated were analysed using descriptive statistics,correlation and regression. The terrain attributes were modified with genetic horizon depths,bulk density and clay content for the modelling process. Sand content, bulk density andcation exchange capacity possess geogenic rather than pedogenic characteristics and werenormally distributed. The indication is that the two groups of terrain attributes depended onthe mass per unit area of soil and clay content in their influence on these ultisol profiles.Paired comparison, root mean square error and normalized root mean square errorindicated that the model was a good fit and could be useful in the prediction of soil propertiesand management of coastal plain sands.