Pedotransfer Functions for Estimating Saturated Hydraulic Conductivity of Selected Benchmark Soils in Ghana

Abstract

Aims: Direct methods of measuring saturated hydraulic conductivity (K s ), either in situ or in the laboratory, are time consuming and very expensive. Several Pedotransfer functions (PTFs) are available for estimating K s , with each having its own limitations. In this study, the performances of four popular PTFs were evaluated on different soil classes in the semi deciduous zone of Ghana. The PTFs considered herein were Puckett et al. (1985), Campbell and Shiozawa (1994), Puckett (1994), andFerrer-Julià et al. (2004). In addition, five local data derived PTFs were used to study the possibility of using local datasets to validate PTF accuracy. Materials and Methods: A total of 450 undisturbed soil cores were collected from the 0 -15 cm depth from three benchmark soils, namely, Stagni-Dystric Gleysol (SDG), Plinthi Ferric Acrisol (PFA) and Plinthic Acrisol (PA). The K s of samples were measured by the falling-head permeameter method in the laboratory. Sand, silt and clay fractions, bulk density, organic matter content, and exchangeable calcium and sodium were measured and used as input parameters for the newly derived PTFs. Accuracy and reliability of the predictions were evaluated by the root mean square error (RMSE), coefficient of correlation (r), index of agreement (d), and the Nash-Sutcliffe efficiency (NSE) between the measured and predicted values from both tested and newly derived PTFs. The relative improvement (RI) of the newly derived PTFs from this study over the existing ones were also evaluated. Results: The newly derived PTFs in this study had higher prediction accuracy with r, d, RMSE and NSE ranging from 0.80 -0.99, 0.79 -0.94, 0.14 -1. 74 and 0.84 -0.98, respectively, compared with 0.32 -0.45, 0.27 -0.50, 4.00 -4.90 and 0.41 -0.47 for the tested PTFs. The relative improvement of the newly derived over the tested PTFs ranged from 56.50 -95.71% in the SDG, 70.73 -96.89% in the PFA, and 65.37 -95.81% in the PA. Generally, RI was observed to be highest for Model 1 in the SDG, and Model 4 in both PFA and PA, and lowest for Model 5 in all three soils. It was observed that the inclusion of exchangeable calcium and sodium as predictors increased the predictability of the newly derived PTFs.

Impact of Land Use Types and Seasonal Variations on Soil Physico-chemical Properties and Microbial Biomass Dynamics in a Tropical Climate, Ghana

“…An area of 300 m 2 was demarcated in each land use type for soil sampling. In each of the 300 m 2 land use type, 5 samples were collected at 0-15 cm soil depth with a soil auger as described by Tuffour et al [13] in each season. In microbial biomass analysis, the upper part of the soil (0-15 cm) is widely considered due to the high presence of microbes and their activities in this zone [4].…”

Prediction of saturated hydraulic conductivity Ks of agricultural soil using pedotransfer functions

“…One of the most important hydraulic properties of each soil is the saturated hydraulic conductivity Ks. It is a widely used characteristic in soil water and solute transport models incorporated in a number of different environmental, hydrological and water management applications (Schaap et al 2001;Araya & Ghezzehei 2019;Tuffour et al 2019). Under most field conditions, soils are not only heterogeneous, but also anisotropic.…”

A comparison of measured and estimated saturated hydraulic conductivity of various soils in the Czech Republic

“…

The saturated hydraulic conductivity of soil (Ks) is one of the most important and most widely-used soil parameters and is commonly applied in a number of different geotechnical, environmental, and water investigations and models (Schaap et al 2001, Mbonimpa et al 2002, Araya and Ghezzehei 2019, Tuffour et al 2019. Ks refers to the ease with which the pores of saturated soil/rock transmit water (United States Department of Agriculture 2022).

…”