| 摘要: |
| 【目的】克服离心机法测定土壤水分特征曲线时“变体积”的缺陷，实现用离心机法获取扰动土壤准确的土壤水分特征曲线。【方法】选取了山西省16种粒径组成、有机质量差别显著的扰动土壤作为研究对象，采用离心机法测定了初始体积相同的各土壤样品在不同转速下的土壤体积含水率、动态变化的土壤体积；采用多元非线性回归模型，描述了以土壤体积含水率、粒径组成、体积质量和有机质质量分数作为自变量描述土壤水吸力的函数关系，并对模型进行了验证与评价。【结果】土壤水吸力的自然对数函数可以表示为土壤砂粒质量分数、黏粒质量分数、土壤体积质量和含水率乘积以及有机质质量分数等土壤属性的线性函数，模型的决定系数达到0.740；模型建模样本平均相对误差为14.460%，验证样本平均相对误差为13.237%，模型预测精度较高；同时发现土壤属性对于曲线的形状与走势的影响不能忽视，其中砂粒质量分数、土壤体积质量和含水率乘积与土壤水吸力负相关，黏粒质量分数、有机质质量分数与土壤水吸力正相关。【结论】因此，本方法构建的模型更符合实际情况，能够提高土壤水力学参数的精度，同时可以克服离心机测量土壤水分特征曲线体积变化的缺点，得到更合理的土壤水吸力和土壤含水率的关系。 |
| 关键词: 土壤水分特征曲线；多元非线性预测模型；离心机法；仿真数值模拟 |
| DOI：10.13522/j.cnki.ggps.2019236 |
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| Method to adjust the soil water retention curve measured using centrifuge apparatus |
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REN Jian, ZHANG Wuping, WANG Guofang, HUANG Mingjing, QIAO Lei
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1.Shanxi Agricultural University, College of Resources and Environment, Taigu 030800, China;2.Shanxi Agricultural University, Software Institute, Taigu 030800, China;3. Arid Farming Research Center, Shanxi Academy of Agricultural Sciences, Taiyuan 030000, China
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| Abstract: |
| 【Objective】Centrifuge is a common apparatus to measure soil water retention curve, but the resultant soil compression is an issue that might compromise its accuracy and reliability. The purpose of this paper it to present a method to correct such inferiorities.【Method】We measured the water retentions of 16 repacked soils with contrasting texture and organic matter (OM) taken from Shanxi province using a centrifuge apparatus. In the experiment, we measured the initial soil volume, dynamic soil volume, as well as water content under different spinning speeds. A multiple nonlinear regression model was derived to describe the dependence of the matric potential on volumetric moisture content, soil particle sizes, volumetric soil mass and OM; it was then verified against the experimental data. 【Result】The logarithm of the matric potential was linearly related to mass fractions of the sand, clay, OM and volume of the water. The accuracy of the model was 74%, with an average relative error of 14.460% for the modelled samples, and of 13.237% for the samples used for verification. It was also found that soil texture affected predictivity of the model. The matric potential was negatively correlated to the mass fraction of sand, volumetric soil mass and water content, but positively correlated to the mass fraction of clay and organic matter.【Conclusion】The nonlinear regression model linking the matric potential to soil water content, with the change in soil volume modified, was able to improve the accuracy of the centrifuge method; it has implications in soil hydraulic parameter measurement. |
| Key words: soil water retention; multiple nonlinear regression model; centrifuge method; virtual numerical simulation |
