Remote sensing of salt affected soils

Remote sensing is an important aid in mapping and surveying salt affected soils. Both spatial and temporal variation can be followed. We emphasize this overview on reflectance properties by sunlight. Thermal infrared information, which can be used to detect hygroscopic characteristics of salts, and microwaves, which give indirectly information on salt are only described briefly. Spectral properties of different salts consisting of chlorides and sulphates are presented. Also calcite spectra are evaluated. This evaluation gives the background to examine possibilities of present day operational satellites and new technologies like imaging spectroscopy. Possibilities of operational systems, working in broad bands are treated separately with direct observations on bare soils and indirect observations on vegetation covered surfaces. In the visible part of the spectrum the high reflectance of salt covered areas is prominent. Bands in the middle infrared give information on moisture content, which is often associated with salt content differences, and some information on type of salts. The overview ends with a discussion on possibilities of future remote sensing system.