Enhancing GPR detection of salt-accumulated layer in oasis terraced fields by seasonal root zone freezing

Abstract

Accurate characterization of salt-accumulated layer (SAL) distribution is crucial for salinity regulation in oasis terraced fields. In salinized soil environments, high salt content leads to signal attenuation and limits the depth of radar wave penetration, which poses significant interpretation challenges. As a result, Ground-penetrating radar (GPR) technology, widely used and effective in conventional soil surveys, has shown limited applicability under such conditions. This study proposes an innovative approach to enhancing GPR detection of SAL by strategically leveraging seasonal root zone soil freezing phenomena. The influence of the main control factors, namely freezing depth, pre-freezing irrigation, and soil salinity level, on the performance of the methodology was systematically evaluated through numerical simulations and field testing. Results reveal that GPR detection of SAL achieved optimal feasibility when conducted during late winter, when the seasonal freezing depth reaches its maximum. Even better results could be expected when conducting the GPR survey over the land with common pre-freezing irrigation for salinity regulation. Moreover, these enhancements are effective for high salinity soils. Finally, a successful application of GPR to map and diagnose the SAL in an oasis terraced field validated the proposed approach, based on positive correlations with freezing depth and soil salinity level. The outcomes of this study not only broaden the application scope of GPR in soil surveying, but also provide a scientific basis for implementing precision irrigation strategies in salinized soil management, thereby contributing to water conservation efforts.