Influence of Organic Matter on the Estimation of Saturated Hydraulic Conductivity

Estimation of soil hydraulic properties by pedotransfer functions (PTFs) can be used in many applications. Some of existing PTFs estimate saturated hydraulic conductivity ( K s ) of the soil, using organic matter (OM) content as one of the input variables. Several authors have shown an increase in K s with increasing OM content, a soil property that presumably improves soil structure. We used three popular PTFs to examine the relationship between OM content and K s We also used data originating from the U.S., Hungary, and the European HYPRES database, to develop additional PTFs with the Group Method of Data Handling (GMDH). It appears that existing PTFs negatively correlate K s with OM content for some soils. We found indications of negative relationship between OM content and K s with the newly developed PTFs both for directly estimated K s , and for K s estimated via the effective porosity of the soil, using a generalized Kozeny–Carman approach. It is not straightforward to define the exact range of soils with the inverse relationship between OM and K s The range appeared to be data set dependent, but it was extensive within the valid input range of each PTF.