Abstract
Soil water retention determines plant water availability and contaminant transport processes in the subsurface environment. However, it is usually difficult to measure soil water retention characteristics. In this study, an analytical model based on a fractional bulk density (FBD) concept was presented for estimating soil water retention curves. The concept allows partitioning of soil pore space according to the relative contribution of certain size fractions of particles to the change in total pore space. The input parameters of the model are particle size distribution (PSD), bulk density, and residual water content at water pressure head of 15,000 cm. The model was tested on 30 sets of water retention data obtained from various types of soils that cover wide ranges of soil texture from clay to sand and soil bulk density from 0.33 g/cm3 to 1.65 g/cm3. Results showed that the FBD model was effective for all soil textures and bulk densities. The estimation was more sensitive to the changes in soil bulk density and residual water content than PSD parameters. The proposed model provides an easy way to evaluate the impacts of soil bulk density on water conservation in soils that are manipulated by mechanical operation.
Highlights
Soil water retention determines plant water availability and contaminant transport processes in the subsurface environment
An analytical model, which is based on a fractional bulk density concept, was presented for estimating soil water retention for the entire range of water pressure head that determines water availability
The proposed model was tested using 30 sets of soil water retention data measured for various textures of soils that had a wide range of soil bulk density from 0.33 g/cm[3] to 1.65 g/cm[3]
Summary
Soil water retention determines plant water availability and contaminant transport processes in the subsurface environment. It is desirable to utilize readily available information, such as soil texture and bulk density, to estimate soil hydraulic p roperties[1,2,3] This kind of approach benefits the development of computationally efficient methods for evaluating soil hydraulic heterogeneity in watershed or agricultural field while ensuring the economic feasibility of field investigation efforts within acceptable accuracy. To improve the mathematical description of physical relations between soil particles and soil pores, we assume that different fractions of soil particles may make different contributions to the total porosity or volumetric water content in the bulk soils and that soil pore volume and associated bulk density are specific for particle size fractions This line of thinking might help derive a better physical model for mathematical estimation of soil water characteristics. The objective of this work was to apply a fractional bulk density (FBD) concept to the development of a soil water retention model that is effective for all soil textures and a wide range of soil bulk density
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