ARTICLE Pedo-transfer function for saturated hydraulic conductivity of lowland paddy soils W. Aimrun Æ M. S. M. Amin Received: 2 July 2008 / Revised: 7 May 2009 / Accepted: 17 May 2009 / Published online: 2 June 2009 Ó Springer-Verlag 2009 Abstract In paddy field, soil saturated hydraulic con- ductivity (K s ) plays as an important component in the calculation of irrigation requirement of the water balance equation and also for irrigation efficiency. Several labora- tory and field methods can be used to determine K s . Labo- ratory and field determinations are usually time consuming, expensive and labour intensive. Pedo-transfer functions (PTF) serve to translate the basic information found in the soil survey into a form useful for broader applications through empirical regression of functional relationships, such as simulation modelling. Since PTFs have not been applied to paddy soils in the study area, a lot of field mea- surements will require high labour input to determine K s hence high cost. This study attempts to seek a simplified method for determining K s values based on common existing soil properties through PTF technique. Soil sam- ples (n = 408 samples) were collected randomly depending on the soil series within the 2,300 ha Sawah Sempadan rice cultivation area. Both field work and laboratory work were carried out. The samples were then analysed for the following properties: dry bulk density (D b ), soil particle percentage (Sand-S, Silt-Si and Clay-C), organic matter (OM) and geometric mean diameter (GMD). The measured K s values were obtained by using the falling head method. The parameters were then used as inputs for developing a K s model by regression analysis using Statistical Analysis System (SAS) package. Stepwise regression analysis was applied to determine the best fit model based on R 2 and significant level. The results of the study showed that there is a high spatial variability of the saturated hydraulic con- ductivity in the paddy area. The best regression model for estimating K s was based on C, D b , OM and GMD with the dependent variable (K s ) in a form of natural logarithm. The model inputs introduced by stepwise regression are com- monly available therefore, this model is useful to replace the conventional method. Keywords Falling head method  Water balance equation  Irrigation requirement  Spatial variability  Stepwise regression analysis Introduction Soil saturated hydraulic conductivity (K s ) is an important soil physical property, especially for determining infiltra- tion rate, irrigation practice, drainage design, run off, groundwater recharge and in simulating leaching and other agricultural and hydrological processes. Several laboratory and field methods can be utilized to determine K s . Unfor- tunately, laboratory and field determinations are usually time consuming, expensive and labour intensive. A study has shown that determining the saturated hydraulic conductivity using Double ring infiltrometer method may require 120 min. Rainfall simulator, Guelph permeameter and Guelph infiltrometer may take 125, 65 and 60 min, respectively (Gupta et al. 1993). Some research results indicate that something in the order of 1,300 measurements would have to be made in a 10-ha field to accurately measure the saturated hydraulic W. Aimrun (&)  M. S. M. Amin Smart Farming Technology Laboratory, Institute of Advanced Technology, 43400 Serdang, Selangor, Malaysia e-mail: aimrun@gmail.com M. S. M. Amin Department of Biological and Agricultural Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia 123 Paddy Water Environ (2009) 7:217–225 DOI 10.1007/s10333-009-0165-y