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| DOI：10.13522/j.cnki.ggps.2019243 |
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| Using Clay Content to Estimate Soil Water Characteristic Curve |
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XIA Tian, TIAN Juncang
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1. School of Civil and Hydraulic Engineering, Ningxia University, Yinchuan 750021, China; 2. Ningxia Research Center of Technology on Water-saving Irrigation and Water Resources Regulation, Yinchuan 750021, China; 3. Center of Engineering Research on Efficient Utilization of Water Resources in Modern Agriculture in Arid Regions (Ministry of Education), Yinchuan 750021, China
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| Abstract: |
| 【Objective】Water retention curve is a parameter describing the ability of a soil to hold water; it is modulated by soil structure and texture. The aim of this paper is to evaluate the feasibility of using clay content to estimate water retention curve of a sandy soil.【Method】The sandy soil used in the experiment was sieved to two groups first, and 12 soils with different clay contents were made by thoroughly mixing soils taken from the two groups at different mass fractions. The water retention curve of each sample was measured in laboratory, from which we calculated the pore size distribution and analyzed the impact of the clay content.【Result】When bulk density was 1.55 g/cm3, increasing clay content by 1.9 times led to a 28.6% decrease in volume of pores with diameters in the range of 0.03~1 mm, and six times increase in volume of pores with diameter in the range of 200 nm~0.03 mm. Fitting the curves to the van Genuchten formula showed that the parameters θs and α in the formula were positively proportional to the clay content, while the parameter θr was negatively proportional to the clay content; the parameter n in the formula decreased exponentially with the clay content.【Conclusion】There were close correlations between all parameters in the van Genuchten formula and the clay content in the sandy soil we studied. These correlations, along with the van Genuchten formula, can be used to estimate the water retention curve of the sandy soil after its clay content changes due to cultivation and/or erosion. For all soils with different clay contents we studied, the absolute errors between the estimated and the observed water contents were less than 15%. These results have implications for numerical simulation of water flow and solute transport in these soils. |
| Key words: clay content; soil; water characteristic curve; model |
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