Lee et al. (2025) Estimation of soil moisture retention using pedo-transfer functions based on soil particle-size distribution and organic matter of Korean soils

Identification

• Journal: Paddy and Water Environment
• Year: 2025
• Date: 2025-12-19
• Authors: Se-In Lee, Seung-Oh Hur
• DOI: 10.1007/s10333-025-01054-3

Research Groups

• Division of Soil and Water Environment, National Institute of Agricultural Sciences, Rural Development Administration (RDA), Wanju, Republic of Korea.

Short Summary

This study developed and validated new pedo-transfer functions (PTFs) specifically for Korean agricultural soils to estimate moisture retention at 10, 33, and 1500 kPa. The resulting models significantly outperformed established international models (Saxton and Saxton-Rawls), providing more accurate tools for regional water management.

Objective

• To develop and evaluate new pedo-transfer functions (new-PTFs) for Korean soils using soil particle-size distribution and organic matter content to predict soil moisture retention at specific matric potentials ($\theta{10}$, $\theta{33}$, and $\theta_{1500}$).

Study Configuration

• Spatial Scale: National scale across South Korea, encompassing 292 soil series from various agricultural landscapes (paddy and upland fields).
• Temporal Scale: Point-in-time soil sampling and laboratory analysis used to build a comprehensive physical property database.

Methodology and Data

• Models used: Multiple Linear Regression (MLR) using Stepwise methods to derive equations. Performance was compared against the Saxton (SM) and Saxton and Rawls (SRM) models.
• Data sources: A dataset of 1,302 soil samples for model development and 138 samples for validation.
• Measured Parameters: Soil particle-size distribution (sand, silt, clay via pipette method), organic matter (OM via Tyurin titration), bulk density (100 $cm^3$ cores), and moisture retention at 10, 33, and 1500 kPa (pressure plate extractor).

Main Results

• Predictor Variables: Silt and clay contents were the primary predictors for $\theta{10}$ and $\theta{33}$, while sand, clay, and OM were required to accurately predict $\theta_{1500}$ (wilting point).
• Quantitative Performance: The new-PTFs achieved $R^2$ values of 0.78 for $\theta{10}$, 0.78 for $\theta{33}$, and 0.65 for $\theta_{1500}$.
• Error Metrics: The models showed lower error than existing PTFs, with Root Mean Square Error (RMSE) ranging from 4.83% to 6.16% and Mean Absolute Error (MAE) from 3.37% to 4.86%.
• Model Efficiency: Nash-Sutcliffe Efficiency (NSE) values were 0.60 for $\theta{10}$ and 0.76 for $\theta{33}$, indicating good performance, whereas established US-based models (SM and SRM) often produced negative NSE values when applied to Korean soils.

Contributions

• Regional Optimization: Addresses the systematic bias and underestimation found when applying US-developed PTFs to the unique soil structures and climatic conditions of the Korean peninsula.
• Agricultural Application: Provides a validated, cost-effective tool for estimating field capacity and wilting points, essential for optimizing irrigation schedules and hydrological modeling in Korean paddy and upland systems.
• Database Utility: Utilizes a large-scale national soil database to improve the interpretability of how fine particles (silt/clay) versus organic matter influence moisture retention at different tension levels.

Funding

• National Institute of Agricultural Sciences, Rural Development Administration (RDA), Republic of Korea.
• RDA Research Project: RS-2021-RD009511.

Citation

@article{Lee2025Estimation,
  author = {Lee, Se-In and Hur, Seung-Oh},
  title = {Estimation of soil moisture retention using pedo-transfer functions based on soil particle-size distribution and organic matter of Korean soils},
  journal = {Paddy and Water Environment},
  year = {2025},
  doi = {10.1007/s10333-025-01054-3},
  url = {https://doi.org/10.1007/s10333-025-01054-3}
}

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