Calibration of capacitance sensor for Andosol under field and laboratory conditions in the temperate monsoon climate
Calibration of capacitance sensor for Andosol under field and laboratory conditions in the temperate monsoon climate
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温带季风气候现场和实验室条件下 Andosol 电容传感器的校准
DOI：
10.1016/j.still.2018.12.020
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发表时间：
2019
影响因子：
6.5
通讯作者：
H.
中科院分区：
文献类型：
--
作者：
Kassaye;K.T.;Boulange;J.;Saito;H.;Watanabe;H.
利用土壤的介电特性，研制了电容式土壤水分传感器。虽然CS在各种类型的土壤中进行校准，但默认校准函数可能不适用于所有条件，因为这种土壤具有高有机质含量，因此，有时需要进行土壤特定校准以达到合理的精度。本研究（1）评价了Decagon 5 T M CS默认校准函数对Andosol（Kuroboku）的适用性，以及（2）推导出的土壤特定校准函数对Andosol的适用性。2016年8月至2017年7月，在Sakaecho（东京西郊）进行了一项实地监测实验，其中使用烘干重量法和安装在5 cm深的CS测量了裸田和重新包装土壤的体积土壤含水量（θv）。当使用默认的工厂提供的校准函数（FSC）时，使用在自然条件和CS下从野外取样的土芯监测的θ v值在野外和实验室条件下都显示出较大的误差。在野外和实验室条件下，这些偏差分别显著（P < 0.001）低估了土芯中测得的θ v，低估幅度为0.117 - 0.199和-0.004-0.131 cm 3 cm − 3。相应地，通过将土壤的介电常数与从土芯样品测量的θ v相关联，开发了特定于土壤的校准函数。根据现场条件下的特定校准函数计算的θ v与观测到的θv最佳拟合。CS校正使θ v测量误差从FSC的15%提高到≤ ± 2%。而实验室校准的改善从FSC的±15%到现场测量数据时的±4%，因此，它仍然低估了观测场θv。现场和实验室程序之间的偏差是由于变形的聚集土壤结构和随之而来的变化，由于破碎时，2毫米的筛子用于样品制备的水力特性。建议在自然条件下对5 T M CS进行准现场标定，以实时监测θvin Andosol。在现场标定不可行的情况下，进一步用现场数据验证的实验室标定也可以提供一种可靠的方法来标定5 T M CS的土壤。
Capacitance sensors (CS) were developed to continuously measure soil water content using the dielectric properties of soils. Although CS are calibrated in soils of various types, the default calibrated functions may not work for all conditions as in the case of this soil that has high organic matter content, hence, soil-specific calibrations are sometimes required to achieve reasonable accuracy. This study (1) evaluated the suitability of the default calibrated functions of a Decagon 5 T M CS for Andosol (Kuroboku), and (2) derived soil-specific calibration functions to Andosol. A field monitoring experiment was conducted at Sakaecho (western suburb of Tokyo) from August 2016 to July 2017, where volumetric soil water content (θv) was measured in bare field and repacked soils using both gravimetric method with oven drying and CS installed at 5 cm depth. The values ofθvmonitored using soil cores sampled from the field under natural condition and CS revealed large errors under both field and laboratory conditions when the default factory supplied calibration function (FSC) was used. The deviations depicted significant (P < 0.001) underestimations of the observedθvmeasured in soil cores by 0.117 - 0.199 and -0.004 - 0.131 cm3cm−3for field and laboratory conditions, respectively. Accordingly, soil-specific calibration functions were developed by correlating the dielectric permittivity of the soil withθvmeasured from the soil core samples. Theθvrecalculated based on the site-specific calibration function under field condition best fitted to the observedθv. Calibration of CS improved theθvmeasurement error from 15% with FSC to ≤ ±2%. Whereas the improvement with laboratory calibration was from ±15% with FSC to ±4% when the function was implemented to the field measured data, hence, it still underestimated the observed fieldθv. The deviation between the field and laboratory procedures was attributed to the deformation of the well-aggregated soil structure and its consequent changes in hydraulic properties due to crushing when a 2-mm sieve was used for sample preparation. Quasi-field calibration of the 5 T M CS under natural condition is highly recommended for real-time monitoring ofθvin Andosol. In cases when field calibration is impractical, laboratory calibration further verified with field data could also offer a reliable method for calibration of the 5 T M CS for Andosols.