Effects of Soil Morphology on Hydraulic Properties II. Hydraulic Pedotransfer Functions

Abstract

Pedotransfer functions (PTFs) have gained recognition in recent years as an approach to translate simple soil characteristics found in soil surveys into more complicated model input parameters. However, existing pedotransfer functions have not yet incorporated critical soil structural information. This study showed that soil hydraulic properties could be estimated from morphological features determined in situ (including texture, initial moisture state, pedality, macroporosity, and root density) through a morphology quantification system. Comparison between the class and continuous PTFs developed in this study indicated that the use of quantified morphological properties yielded predictive power similar to that of physical properties in estimating hydraulic conductivity at zero potential; water flow rates in macro‐, meso‐, and micropores; and a soil structure and texture parameter αmacro The results confirmed that soil structure was crucial in characterizing hydraulic behavior in macropore flow region; whereas texture had major impact on those hydraulic properties controlled by micropores. Depending on the flow domain to be included, estimation of hydraulic properties required the use of different combinations of morphometric indices or physical properties. The PTFs established may be used as starting points for estimating model input parameters.

Hydropedology and pedotransfer functions

“…bdummy codingQ (McCullagh and Nelder, 1989), could be used provided the misclassification errors are known. A version of the dummy coding was successfully used by Lin et al (1999) to estimate Ksat from morphometric indices.…”

The impact of available water content in previous agricultural soils on tree growth and nutritional status in young hybrid aspen plantations in Estonia

“…In addition to the texture layering that we also established on automorphic soils, looser topsoil structure (lower BD in Supplementary Table 2) appeared on drained Gleysols. Soil structure was crucial in characterizing hydraulic behaviour in the macropore flow region, whereas texture had major impact on those hydraulic properties controlled by micropores (Lin et al 1999). Due to drastic pores discontinuity between humus horizon and reductomorphic mineral subsoil, if their topsoil dried up during drought, then rewetting of Gleysols would be remarkably slower.…”

An infiltration model based on flow variability in macropores: development, sensitivity analysis and applications

“…Since most PTFs do not incorporate critical soil structural information (Lin et al, 1999a), the predictions for the organic, structure rich A-horizon are quite uncertain for conventional PTFs. Therefore, a 'class PTF' to estimate the hydraulic conductivity for flow in micropores was used to estimate the hydraulic conductivity of the soil matrix for the top layer (Lin et al, 1999b). These class PTFs use textural and morphometric information together with root density and content of organic matter.…”