Performance Evaluation of Pedotransfer Functions to Predict Field Capacity and Permanent Wilting Point Using UNSODA and HYPRES Datasets

Abstract

Using basic soil properties could save time and costs in determining field capacity (FC) and permanent wilting point (PWP). The objectives of this study were to investigate the relationship between FC and PWP and basic soil properties, develop two new equations for estimating FC and PWP, and evaluating their performance as compared to some existing pedotransfer functions (PTFs) in predicting FC and PWP. For this purpose, 210 soil samples of UNSODA dataset and 45 soil samples of HYPRES dataset were used for development and validation of the PTF, respectively. Graphical exploration of relations between soil texture component, geometric mean particle-size diameter (dg), bulk density (BD), and organic matter (OM) with FC and=or PWP showed that relations of FC was nonlinearly related to percentage of clay (positive) and dg (negative) and relations of PWP was linearly and nonlinearly related to percentage of clay (positive) and dg (negative), respectively. Based on standardized independent variable weight (W), dg showed the highest influence on FC (W ¼ 0.81), followed by percentage of clay (W ¼ 0.70), OM and BD (W ¼ 0.49). PWP was primarily affected by percentage of clay (W ¼ 0.89) and dg (W ¼ 0.64), whereas BD and OM with Wof 0.30 were less effective. The two new functions suggested and evaluated for predicting FC and PWP had root mean squares error (RMSE) of 0.06 and 0.02 m 3 m À3 , geometric mean error (GMER) 1.03 and 1.10 m 3 m À3 and Akaike's information criterion (AIC) of À262 and À349, respectively. As such, their prediction performance was higher than that of other FC and PWP PTFs found in literature.

Characterizing physical and hydraulic properties of soils in Al-Ahsa, Kingdom of Saudi Arabia

“…Despite FC and WP were significantly correlated with sand% , silt% , ρ , and θ s , only θ s offered a significant F test at 95% confidence interval. These findings were supported by previous works except with the absent of organic matter effect ( Gao and Sun, 2017 ; Mbah, 2012 ; Ostovari et al, 2015 ; Shiri et al, 2017 ). Equations (8 and 9) achieved high correlation associated with low MSE for both training and validation sets.…”

Interactions between soil structure dynamics, hydrological processes, and organic matter cycling: A new soil‐crop model

“…In principle, f mic(text) could be estimated using one of several models that predict the soil pore size distribution from the particle size distribution (e.g., Arya & Heitman, 2015;Chang et al, 2019;Mohammadi & Vanclooster, 2011). However, USSF employs a simpler empirical approach to estimate f mic(text) which makes use of the observation that the water content at wilting point is usually strongly correlated with clay content but hardly at all with organic matter content (e.g., Kätterer et al, 2006;Ostovari et al, 2015;Pollacco, 2008). For the Brooks-Corey water retention model that is employed in USSF (see Equation ( 38) in "Soil hydraulic properties"), we can write:…”

“…where ψ w (m) is the wilting point pressure head (= À150 m) and the corresponding water content θ w (m 3 m À3 ) is estimated from the pedotransfer function derived by Ostovari et al (2015) for European and North American soil data in the HYPRES and UNSODA databases:…”

Influence of Multi-Layered Structure of Vadose Zone on Ecological Effect of Groundwater in Arid Area: A Case Study of Shiyang River Basin, Northwest China

“…However, the available water content of the soil column after water release still needs to be discussed. It is well known that not all of the water in the soil can be used by vegetation, and the available water content is determined by the field capacity and the permanent wilting point [35][36][37][38]. According to the method in reference [39], when the soil pressure head is −1.5 MPa, the corresponding water content is at permanent wilting point.…”