Calibrating Access‐tube Time Domain Reflectometry Soil Water Measurements in Deep Heterogeneous Soils
Calibrating Access‐tube Time Domain Reflectometry Soil Water Measurements in Deep Heterogeneous Soils
复制标题
校准深层异质土壤中的接入管时域反射法土壤水测量
DOI：
10.2136/sssaj2007.0208
复制
发表时间：
2008
影响因子：
2.9
通讯作者：
J. Rimstidt
中科院分区：
文献类型：
--
作者：
Benjamin F. Schwartz;Madeline E. Schreiber;P. S. Pooler;J. Rimstidt
渗透带的水文特征需要在各种土壤质地中精确测量土壤水分。时域反射仪（TDR）是测量土壤湿度的常用仪器。尽管使用热带病防治有优势，但某些类型的仪器带来了挑战，包括正确安装和校准，必须克服这些挑战。本研究的主要目的是开发一种新的方法来获取和校准非均质深层土壤的通道管TDR测量值。利用两种回归技术，开发了基于物理和化学性质的校准来预测土壤水分，并解释了TDR和重力土壤水分值之间的巨大差异。TDR土壤水分与重测土壤水分差异几乎完全由土壤理化性质控制；这表明我们的导管TDR探针可能产生了“自由”而不是结合水含量的准确测量。结合分数受物理和化学性质控制，在本研究考虑的深度和时间尺度上是一个几乎静态的参数。初始校准后TDR测量值的变化表示“自由”水含量的变化。我们的校准方程使用容易获得的参数来预测广泛土壤质地下的准确土壤水分值。使用我们的校准方程预测的大约95%的土壤水分值的残差小于±10%的土壤水分。我们还开发了一种具有成本效益的安装管道的方法，该方法最大限度地减少了深层土壤剖面中与气隙和土壤结构干扰有关的问题。
Hydrologic characterization of the vadose zone requires accurate measurements of soil water in a variety of soil textures. Time domain reflectometry (TDR) instruments are commonly used to obtain soil moisture. Although there are advantages to using TDR, certain types of instruments pose challenges, including proper installation and calibration, which must be overcome. The principal objective of this study was to develop a new method for obtaining and calibrating access-tube TDR measurements in deep heterogeneous soils. Using two regression techniques, physical and chemical property-based calibrations were developed to predict soil water and explain large differences between TDR and gravimetric soil water values. Differences between TDR soil water and gravimetric soil water were almost entirely controlled by physical and chemical soil properties; indicating that our access-tube TDR probe likely produced an accurate measurement of 'free' but not bound water content. The bound fraction is controlled by physical and chemical properties and is a nearly static parameter at the depths and time scales considered in this study. Changes in TDR measurements after the initial calibration represent changes in the 'free' water content. Our calibration equations used easily obtained parameters to predict accurate soil water values in a wide range of soil textures. Approximately 95% of the soil water values predicted using our calibration equations had residuals of less than ± 10% soil water. We also developed a cost-effective method for installing access tubes which minimized problems related to air gaps and soil structure disturbances in deep soil profiles.