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Title: FUNCTIONAL EVALUATION OF PEDOTRANSFER FUNCTIONS DERIVED FROM DIFFERENT SCALES OF DATA COLLECTION

Author
item NEMES, ATTILA - HYDROLOGY LAB, ARS, MD.
item SCHAAP, MARCEL - UC RIVERSIDE, CA
item WOSTEN, HENK - ALTERRA, THE NETHERLANDS

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2003
Publication Date: 7/20/2003
Citation: Nemes, A., Schaap, M.G., Wosten, H. 2003. Functional evaluation of pedotransfer functions derived from different scales of data collection. Soil Science Society of America Journal. 67:1093-1103.

Interpretive Summary: Soil hydraulic properties are required for studies of fluid and/or solute transport in soils. However, measurement of soil hydraulic properties is not easy and often impossible for large area's of land. Soil hydraulic properties can also be estimated using statistical models that use easily measurable soil parameters as predictors. Such models are often called pedotransfer functions (PTF) and may serve an important role in cases where soil hydraulic properties cannot be measured. This study investigates whether PTFs that were developed on global and continental-scale datasets are accurate enough to be applied on the scale of a medium-sized country (Hungary). Although the errors for global and continental scale PTFs are somewhat larger than the ones developed specifically for Hungary, they are generally admissible. The importance of this study is that it demonstrates that it is possible to use already available global-scale PTFs for smaller national scales. This would enable researchers in small countries having limited resources to estimate soil hydraulic properties.

Technical Abstract: The measurement of soil hydraulic properties is often difficult, time-consuming and expensive. Therefore, many studies have been conducted in the past yielding models, also called pedotransfer functions (PTFs), to estimate soil hydraulic properties from surrogate data, such as texture and bulk density. However, most of these models are empirical and it is often unclear whether PTFs that were developed for one group of soils are applicable to other soils. This study evaluates the performance of PTFs developed for a global data set and a European dataset on the national soils database of Hungary. Prediction errors were low for the Hungarian PTF (0.02 to 0.06 cm3/cm3) while the European and International PTFs generated somewhat larger errors (0.025 to 0.088 cm3/cm3). It is concluded that international PTFs can be applied on national scales if appropriate care is taken. Estimated retention curves were used to simulate soil moisture time series in Hungary. Root mean square residuals during a growing season ranged from 0.065 to 0.07 cm3/cm3. When measured data were used the error was only slightly smaller (0.061 cm3/cm3).