The aim of this study was to evaluate the behavior of the soil line for different soil classes by using reflectance data with a spectroradiometer in the laboratory. Representative samples of the surface and subsurface horizons of 18 soil classes collected in a pilot area in Rafard county, southwest São Paulo state, were dried, sieved and accomodated for spectral reading. Data were computed in order to simulate TM-Landsat 3 and 4 bands and to draw the graphs. The findings showed that the soil lines obtained for the samples of both soil layers behave similarly and are distributed orthogonal to the graph axes with R² values at about 1.0 for all classes evaluated. It was observed that there is not a unique soil line, and the data suggest that each soil has an individual line and features. In addition, the use of such an index can be an auxiliary method for discriminating soil classes, since sandy soils, with a lower iron content were different from the more clayey ones with a higher iron content, besides presenting higher reflectance values. Finally, it was observed that the organic matter was not a determinant factor regarding the spectral behavior in relation to the soil line.
Reflectance; vegetation index; spectral behavior; iron; clay
