Evaluation of red soil drought index based on dielectric spectrum characteristic parameters
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DOI:10.7606/j.issn.1000-7601.2024.01.27
Key Words: red soil  frequency domain dielectric spectroscopy  characteristic parameter  volumetric water content  drought index
Author NameAffiliation
WANG Haijun College of Water Conservancy, Yunnan Agricultural University, Yunnan, Kunming 650201, China 
XU Xingqian College of Water Conservancy, Yunnan Agricultural University, Yunnan, Kunming 650201, China 
QU Xin School of Civil and Construction Engineering, Henan Anyang Institute of Technology, Anyang, Henan 455000, China 
ZHAO Xi College of Water Conservancy, Yunnan Agricultural University, Yunnan, Kunming 650201, China 
WANG Nenglong College of Water Conservancy, Yunnan Agricultural University, Yunnan, Kunming 650201, China 
CAO Han College of Water Conservancy, Yunnan Agricultural University, Yunnan, Kunming 650201, China 
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Abstract:
      The purpose of this study was to obtain the response characteristics of red soil moisture content to the dielectric spectrum of electromagnetic wave and discuss the feasibility of dielectric spectrum characteristic parameters as the evaluation red soil drought index. The frequency domain dielectric spectroscopy (FDS) test of red soil with different volume water content was finished, and the integral value of the dielectric spectrum characteristic curves was extracted to analyze the correlation between the dielectric spectrum characteristic parameters and the volume water content. Combined with the national agricultural drought grade standard, the red soil drought evaluation indexes based on dielectric spectrum characteristic parameters were proposed. The results showed that the real and imaginary parts of the dielectric constant of red soil gradually decrease with the increase of the frequency of the dielectric spectrum, and both were positively correlated with the volumetric water content. The dielectric loss factor fluctuates with the increasing frequencies, the smaller the volumetric water content, the stronger the fluctuation, and a trend of decreasing first and then increasing was showed. The quantitative relationship between the characteristic parameters of the dielectric spectrum and the volumetric water content was given by the least square method. The bacterial foraging algorithm was used to determine the optimal model coefficients, and the fitting accuracy was greater than 0.95. Finally, the evaluation model of red soil drought index was established based on the characteristic parameters of dielectric spectroscopy. The error between the predicted value and the standard value was between ±1%. The model could effectively evaluate the degree of red soil drought degree to provide the reference indicators for regional agricultural drought investigation, assessment, and early warning in red soil.