Development of pedotransfer functions for coastal plain soils using terrain attributes

This study investigated the influence of terrain attributes and soil water content on soil genesis and developed pedotransfer functions (PTFs) for the coastal plain soils. A two-stage sampling procedure was adopted in the study. In the first stage, a total of 408 samples were collected along twelve toposequences, while in the second stage, 64 representative soil samples were collected on typical upper, middle and lower slope positions. Particle size fractions, bulk density, hydraulic conductivity, organic carbon, field capacity water content (FWC), permanent wilting point (PWP), and available water content (AWC) were determined. Elevation, slope, aspect, curvatures, flow direction and hill shade, compound topographic index (CTI) and stream power index (SPI) were derived from a digital elevation model. The data were analyzed using correlation, principal component and stepwise multiple regression. There was significant correlation (p < 0.01) between FWC and hill shade and CTI. Permanent wilting point and AWC significantly correlated (p < 0.01) with aspect, tangent curvature and CTI. Principal components classified were permeability, retention, solute distribution, soil water stress, soil water loss, and solute transport and water storage factors. Soil water content and saturated hydraulic conductivity were modeled and root mean square error (RMSE) ranged from 0.01 to 2.31%, indicating high predictability. Rainfall intensity was estimated at 0.82 cm h− 1, while the saturated hydraulic conductivity was 0.23 cm h− 1 indicating that 256.5% of the rainfall results in overland flow and redistribution of material. The role of terrain attributes involves the development of pedogenic structural and textural features and movement of clay downslope more laterally than vertically within the landscape.