In-situ Identification of the Thickness of Black Soil Layer based on Ground Penetrating Radar

Objective The traditional acquisition of the thickness of black soil layer highly relied on the field soil profile excavation, which is difficult to investigate and sample. In this study, the Ground Penetrating Radar (GPR) was utilized to conduct the detection of thickness of black soil layer in-situ in the typical black soil region of northeast China. The accuracy and applicability of identification were also evaluated through the soil profile survey.

Method Two different sampling methods, automatic gain and high gain from 30 typical black soil profiles, were used to process root-mean-square error gain of radar data in the later stage, to analyze the identification accuracy of GPR, and to explore the influence of black soil layer thickness, slope, parent material and crop type on the identification accuracy.

Result ① The detection rates of black soil layer thickness for the automatic gain and high gain samples were 57.6% and 96.6%, and the determination coefficients were 0.97 and 0.80. ② The identification efficiency decreased with the increase of the thickness of black soil layer. The detection accuracy of GPR for thin black soil (0-30 cm) and middle black soil (30-60 cm) were higher, with R² values of 0.93 and 0.91. The detection accuracy for thick layer black soil (60-120 cm) was relatively lower, with R² of 0.72 and 0.61 for the two sampling methods. ③ The higher GPR identification accuracy were found in soybean fields, steep slopes (6º-15º) and non rocky-material areas.

Conclusion GPR had good accuracy and applicability for in-situ identification of black soil layer. The latter data processing could improve the efficiency and accuracy of GPR identification accuracy of the thickness of black soil layer. Using GPR in areas with minimal disturbance to the surface root system, steep slopes, and uniform parent material could improve its detection accuracy of the thickness of black soil layer.