SPECTRAL DISCRIMINATION OF BRAZILIAN PLATEAULATOSOLS

Remotely sensed imagery serves as a tool for accelerating soil survey activity to the extent that features in the imagery can be related to soils in their landscape. This has been clearly proven for discriminat ion of broad geomorphic units in Landsat and SPOT imagery. However, fa rm-level soil mapping is likely to require discrimination of soil unit s at a scale where topographic clues are not enough for class separati on. The capability to distinguish soil classes in remote imagery is ve ry much related to inherent spectral behavoir of diagnostic soil compo nents. This is especially true in Brazil where soil color is used for class definition, principally as a covarying property with iron oxide form and content. This study investigated the potencial for soil spect ral discrimination of a chromosequence of latosols (oxisols), from the Central Plateau of Brazil, using a portable field radiometer sensitiv e in the 380-875 nm reflective wavelength range. Pairwise comparison o f spectral reflectance of soils reveals wavelength regions of maximum spectral discrimination, accentuating the 450-520 nm (blue) region of opaque behavior of the hematite-rich Dark-Red Latosol (LE) in contrast to the goethite rich Red-Yellow Latossol (LV).