LARS Tech Report Number
Many attempts have been made to use multispectral data to map soils on the basis of soil color, texture, organic matter content, moisture content, and free iron oxides. Researchers have endeavored to differentiate soil series and coil types, using those parameters individually. Reflective properties have been attributed primarily to one or two of these parameters. Little has been revealed as to the nature of the natural interactions occurring between those parameters. Scientists have suggested that a more complete understanding of the radiation properties of specific soil constituents and their interactions is needed before one can optimize the use of multispectral separability in differentiating soil series and soil orders.
The objectives of this study are twofold: (1) To evaluate quantitatively the effects of organic matter, free iron oxides, texture, moisture content, and cation exchange capacity on the spectral reflectance of soils, and (2) to develop and test techniques for differentiating soil orders by computer analysis of multispectral data.
By collecting 71 soil samples of benchmark soils from the different climatic regions within the United States (having different vegetative cover types, parent materials, and geological history) and using the extended wavelength field spectroradiometer (Exotech Model 20B) to obtain reflectance values and curves for each sample, average curves were constructed for each soil order (excluding Oxisols and Histosols).
Multiple regression analyses were performed, using the spectral data as the dependent variables and physical - chemical properties as independent variables. The independent variables showing the highest correlation with the multispectral measurements were CEC and silt content. These results suggest that multispectral analysis may be a valuable tool for delineating and quantifying differences between soils.
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