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| DOI：10.13522/j.cnki.ggps.2017.0553 |
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| Relationships between Bulk Density, Water Content and Matric Potential of Soils During Drying Process |
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NIE Weibo , XING Xuguang
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Institute of Water Resources, Xi’an University of Technology, Xi’an 710048, China; College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China
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| Abstract: |
| 【Objective】 Wetting-drying cycles affect soil physical properties and this paper is to investigate how the bulk density, water content and matric potential of soils are correlated when the soils are shrunken during drying process. 【Method】 Soil samples were taken from Liaoning (sandy loam), Yunnan (clay loam), Shaanxi (slay loam) and Shandong Provinces (loam). We first measured the water release curve using the centrifuge method for each soil and then fitted it to the Brooks-Corey formula. We thereafter investigated the soil shrinkage during drying process and analyzed the relationship between bulk density, water content and matric potential of the soils.【Result】 The soil moisture decreased with an increase in matric potential, and the decreasing rate decreased first, then increased, followed by a decrease with the matric potential increasing from 0 to 7 000 cm. A power function was found between the soil bulk density and the matric potential based on the Brooks-Corey formula for water retention and the linear model for soil shrinkage. The decrease in water content due to increase in bulk density can be described by the soil shrinkage curve which is piecewise linear in the pseudo-saturated stage, the structural change stage and the super-normal stage, each corresponding to a specific matric potential range depending on soil types. 【Conclusion】 The relationship between the bulk density and the matric potential follows a power and can be fitted to the logistic model. |
| Key words: soil drying; bulk density; soil moisture; matric potential; Brooks-Corey model |
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