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 both 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 soil 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 implement 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 0.15 m soil depth was 7.81 × 10–7 m·s–1. Further, for a given soil texture the variability, from 2.30 × 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 when using the measured input data and thus calculated values of Ks can be used as input in simulation models.
Highlights
In order to model soil physical processes related to soilwater content, it is important to know the hydraulic properties of the soil [1]
There were three textural classes corresponding to the 18 spots where undisturbed soil samples were taken (Figure 2) and these were: clay loam, sandy clay loam, and sandy clay
The field has five distinct areas with oil wells and access roads that are not cultivated. These areas were included in our analysis as they contribute to the hydrological processes of the entire field, and were assigned a textural class of sandy clay
Summary
In order to model soil physical processes related to soilwater content, it is important to know the hydraulic properties of the soil [1]. Vigiak et al [2] remarked the importance of characterizing soil hydraulic parameters in order to understand the occurrence and movement of overland flow at field, hill-slope, and catchment scale. These soil hydraulic properties include the saturated (Ks) and unsaturated hydraulic conductivity, and the water retention curve. Examples of two simulation models that require soil hydraulic properties as inputs are the Energy Water Balance. Soil hydraulic properties are a required input in models used to calculate water runoff and soil erosion, e.g. Precision Agricultural Landscape Modeling System [8,9,10] and examples of other models are given by Aksoy and Kavvas [11]
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