Test of the Rosetta Pedotransfer Function for saturated hydraulic conductivity

Authors: ALVAREZ-ACOSTA, CARLOS - Wageningen University; Lascano, Robert; STROOSNIJDER, LEO - Wageningen University

Submitted to: Trade Journal Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2012
Publication Date: 9/1/2012
Citation: Alvarez-Acosta, C., Lascano, R.J., Stroosnijder, L. 2012. Test of the Rosetta Pedotransfer Function for saturated hydraulic conductivity. Open Jouranl of Soil Science. 2(3):203-212.

Interpretive Summary: The use of simulation models as tools to manage different aspects of agricultural systems continue to gain popularity. This renewed interest is due to the decreased cost of computer hardware that is needed to run these models and the increased availability of public-domain databases that provide many of the input data required to run these models. Information on hydraulic properties of soils is an important input parameter that is normally needed in all type of hydrological models. The soil hydraulic properties refer to 1) saturated hydraulic conductivity (Ks); 2) the relation between the soil water content and the energy required to remove the water; and 3) the soil water content and the speed at which water moves in the soil. These three properties can be measured under laboratory and field conditions; however, their measurement is tedious, expensive and time consuming. Because of these impediments soils scientists developed what is known as pedotransfer functions (PTFs) as a means to calculate soil properties that are normally difficult to measure. The basic premise of PTF is to use soil properties that can easily be measured and these in turn are used to calculate soil properties that are difficult to measure. Further, PTF’s use a hierarchical approach, which means that each level uses more measured parameters and that each level is additive, i.e., level 3, uses the parameters used in level 2 and in level 1. A popular PTF to calculate soil hydraulic properties is named Rosetta developed by soil scientists at the University of California, Riverside. Our objective was to test Rosetta as a predictor of Ks for a soil near Lamesa, TX using different levels on input parameters that are easily measured. We started with soil texture, adding soil bulk density, adding laboratory measurement of the soil water content at field capacity and finally adding laboratory measurement of the soil water content at the wilting point. We evaluated the calculated valued of Ks at the different levels by comparing these values to measured values of Ks. This comparison yielded and as expected that the higher level of inputs the better the results would be. We concluded that the Rosetta PTF can be used to estimate values of Ks for the soil we used in our experiments and these values of Ks can be used as input to simulation models.

Technical Abstract: Simulation models are tools that can be used to explore, for example, effects of cultural practices on soil erosion and irrigation on crop yield. However, often these models require many soil related input data of which the saturated hydraulic conductivity (Ks) is one of the most important ones. These data are usually not available and experimental determination is expensive and time consuming. Therefore, pedotransfer functions are often used, which make use of simple and often readily available soil information to calculate required input values for models, such as soil hydraulic values. Our objective was to test the Rosetta pedotransfer function to calculate Ks. Research was conducted in a 64-ha field near Lamesa, Texas, USA. Field measurements of texture and bulk density, and laboratory measurements of soil water retention at field capacity (– 33 kPa) and permanent wilting point (– 1500 kPa), were taken to execute Rosetta. Calculated values of Ks were then compared to measured Ks on undisturbed soil samples. Results showed that Rosetta could be used to obtain values of Ks for a field with different textures. The root mean square difference (RMSD) of Ks at 15 cm soil depth was 7.81 ' 10-7 m s-1. Further, for a given soil texture the variability, from 2.3 ' 10-7 to 2.66 ' 10-6 m s-1, of measured Ks was larger than the corresponding RMSD. We conclude that Rosetta is a tool that can be used to calculate Ks in the absence of measured values, for this particular soil. Level H5 of Rosetta yielded the best results with the least amount of measured input data and thus can be used as input in simulation models.