时域反射仪(TDR)测定土壤含水量标定曲线评价与方案推荐

Evaluation and analysis of TDR calibration curves for soil water content measurement

时域反射仪(Time Domain Reflectometry)可用于室内和田间快速、准确、自动测定土壤含水量,是目前应用最广泛的土壤含水量测定方法之一。适宜的土壤含水量标定曲线(即土壤表观介电常数和土壤含水量之间的关系)是TDR准确测定土壤含水量的关键。目前文献中存在大量的土壤含水量标定曲线,但尚未有研究对这些标定曲线进行系统的验证和分析评价。因此,它们的准确性和适用范围尚不明晰,严重影响到与土壤含水量测定相关的研究。通过查阅大量国内外文献,收集整理了一系列土壤含水量标定曲线的经验公式(19个)和半经验半物理模型(5个),并利用大量的文献实测数据对其进行综合评价。同时运用均方根差(RMSE),平均误差(AD),纳什效率系数(NSE)等三个指标对比分析和评价这些标定曲线的准确性和可靠性。研究结果表明:经验公式中Topp、Roth(1992)2、Jacobosen、Yoshikawa2、Alharathi模型和半经验模型中Malicki1公式及其修订模型综合性能较好。研究成果可为利用TDR准确测定土壤含水量及土壤含水量标定曲线的选择提供参考和指导。

As a rapid,accurate and economic way for measuring soil water content,time domain reflectometry(TDR)has been widely used around the world.Appropriate TDR calibration curve(i.e.,the relationship between the soil apparent dielectric constant and soil water content)is critical for the accurate measurement of soil water content.At present,many TDR calibration curves are available in literature and the accuracy of the soil water measurement is largely determined by the choice of TDR calibration curves.However,no study attempted to systematically verify or assess their performance.The objectives of the study were therefore to collect the available empirical and semi-empirical formulas in literature,and evaluate them with a compiled high quality literature data.A total of 19 empirical models and 5 semi-empirical models were collated.Their performances were evaluated by three indices including the root mean squared error(RMSE),average deviation(AD),and NSE.The result showed that the formulas of Jacobsen,Topp,Roth(1992)2,Jacobosen,Yoshikawa2,Alharathi and four Malicki functions have the best performance based on NSE,AD and RMSE indices.Because of the nature of empirical models,empirical and semi-empirical TDR calibration curves can only be used for certain types of soils tested.The reader are encouraged to test or establish new calibration curves using the recommended calibration curves with new parameters for soils not mentioned in this study.The result of this study will contribute to the appropriate selection of TDR calibration curves for accurate measurement of soil water content.