Estimating Available Water Capacity from basic Soil physical Properties -A comparison of common Pedotransfer Functions Kai Lipsius 22.07.2002 Studienarbeit, under supervision of Prof. Dr. W. Durner 1 Managed by Dr. Michael Sommer, Dipl. geoökol. Matthias Zipprich2 2 GSF-National research centre 1 Department of Geoecology for environment and health Braunschweig Technical University Studienarbeit Kai Lipsius 2002: Comparison of Pedotransfer Functions II Contents 1 Abstract ........................................................................................................................................... 1 2 Introduction ..................................................................................................................................... 2 2.1 The task ..................................................................................................................................2 2.2 Soil-water Storage..................................................................................................................2 2.3 Available water capacity ........................................................................................................3 2.4 Field capacity .........................................................................................................................3 2.5 Permanent wilting point .........................................................................................................3 2.6 Factors Affecting Moisture Storage .......................................................................................4 2.6.1 Soil Texture .............................................................................................................. 4 2.6.2 Soil structure............................................................................................................. 4 2.6.3 Clay content..............................................................................................................4 2.6.4 Organic matter content ............................................................................................. 5 2.6.5 Depth of wetting and antecedent moisture ............................................................... 5 2.6.6 The presence of impeding layers in the profile ........................................................ 5 2.6.7 Evapotranspiration.................................................................................................... 5 2.6.8 Bulk density.............................................................................................................. 5 2.6.9 Rock fragments......................................................................................................... 5 2.7 Newer Concepts of Soil Water Availability to Plants............................................................5 2.8 Water Retention Curve...........................................................................................................6 2.8.1 Parameterisation of the Water Retention Curve ....................................................... 6 2.8.2 Hysteresis ................................................................................................................. 6 2.9 Pedotransfer Functions...........................................................................................................7 2.9.1 PTF Group A -Direct Prediction of available water capacity................................... 7 2.9.2 PTF Group B -Prediction of water contents at specific points of the WRC............. 7 2.9.3 PTF Group C -Prediction of parameters of the soil water characteristic.................. 8 2.10 The effective AWC ................................................................................................................9 3 Materials and methods................................................................................................................... 10 3.1 Soils and sampling strategies ...............................................................................................10 3.1.1 Texture.................................................................................................................... 11 3.1.2 Organic Carbon content.......................................................................................... 11 3.1.3 Bulk density............................................................................................................ 11 3.1.4 Water Retention Curves (WRC)............................................................................. 12 3.2 Prediction of bulk density.....................................................................................................12 3.3 Prediction of organic carbon content....................................................................................15 3.4 Gravel Volume .....................................................................................................................15 3.5 Pedotransfer Functions.........................................................................................................16 3.5.1 Scheinost 1 (Sch1).................................................................................................. 16 3.5.2 Scheinost 2 (Sch2).................................................................................................. 16 3.5.3 Scheinost 3 (Sch3).................................................................................................. 17 3.5.4 Scheinost 4 (Sch4).................................................................................................. 17 3.5.5 Scheinost and Sinowski (S.S)................................................................................. 17 3.5.6 Sinowski (Sin) ........................................................................................................ 17 3.5.7 Rawls (Rawls) ........................................................................................................ 17 3.5.8 Vereecken 1 (V1) ................................................................................................... 17 3.6 Statistical Methods ...............................................................................................................17 4 Results and discussion................................................................................................................... 19 4.1 Available Water Capacity between –60 hPa and –15000 hPa..............................................19 4.2 Available Water Capacity between –100 hPa and –15000 hPa............................................22 4.3 Available Water Capacity between –300 hPa and –15000 hPa............................................25 5 Conclusions ................................................................................................................................... 29 6 Reference....................................................................................................................................... 30 7 Appendix ....................................................................................................................................... 31 7.1 FAM data base.......................................................................................................................... Studienarbeit Kai Lipsius 2002: Comparison of Pedotransfer Functions III 7.2 S-Plus Programs ...................................................................................................................31 7.2.1 Scheinost und Sinowski.......................................................................................... 31 7.2.2 Scheinost 1.............................................................................................................. 31 7.2.3 Scheinost 2.............................................................................................................. 32 7.2.4 Scheinost 3.............................................................................................................. 32 7.2.5 Scheinost 4.............................................................................................................. 33 7.2.6 Sinowski ................................................................................................................. 33 7.2.7 Rawls ...................................................................................................................... 33 7.2.8 Minasny .................................................................................................................. 34 7.2.9 Renger..................................................................................................................... 35 7.2.10 Vereecken 1............................................................................................................ 36 7.2.11 Vereecken 2............................................................................................................ 37 List of Tables Table 2.1: Soil property ranges of the calibration data sets used to develop the evaluated PTF. Arithmetic means are given in parentheses. .......................................................................... 7 Table 3.1: Parameters of the multiple linear regression for Equation 3.1 for all layers........................ 13 Table 3.2: Statistical results of the multiple linear regression to estimate bulk density........................ 15 Table 4.1: Summary of the performance of the different PTF to predict the AWC [cm3/cm3] between 60 and 15000 hPa ................................................................................................................19