Characterization of soil's structural crust by spectral reflectance in theSWIR region (1.2-2.5 mu m)

Structural crust is a thin layer formed on the soil surface after a rainsto rm. The crust is the result of a physical segregation and rearrangement of soil particles in a way that affects some of the soil properties, such as i nfiltration, runoff and soil erosion. In practice, there is no rapid, in si tu method for monitoring, assessing and mapping crust intensity and quality . In this study, a controlled spectral investigation of the structural crus t across the NIR-SWIR spectral region was conducted on three selected Israe li soils, to study the potential of reflectance radiation to detect structu ral crust in soils. Two major factors served as the driving forces for this study: (1) there is no valid method for in situ assessment of the crust's characteristics in the agriculture field, and (2) the crust might bias them atic remote sensing of soils, because the thin layer of crust blocks photon -matter interaction, which represents the relevant soil body. Through the u se of a laboratory rainfall simulator and a sensitive spectrometer, it was revealed that for three selected soils, significant spectral differences oc curred between the crust and its bulk soil. The spectral information was fo und to be related to changes in particle size distribution and texture at t he surface of the soil. This conclusion was based on indications of absorpt ion of OH in clay lattice, OH in adsorbed water and CO3 in carbonates. It w as concluded that the structural crust is a phenomenon that should not be i gnored by remote-sensing users. In fact, in the field of agriculture, the s pectral properties of crust can be used as tools for estimating the crust's intensity.