Reflectance Technique for Predicting Soil Organic Matter
1980
The objective of this research was to study the spectral reflectance of the selected soils in the infrared and visible wavelength regions and to identify optimal wavelengths for predicting the soil's organic matter content. Samples representative of soils of different texture and predicted organic matter content were collected from different areas in Illinois. Measurements of the spectral reflectance of soil samples in the infrared and visible wavelengths regions were recorded with a multipurpose computerized spectrophotometer with a Cary Model 14 monochromator attachment operated in a single beam mode. A stepwise multiple linear regression program was used to analyze the reflectance data and to determine the optimum wavelengths for predicting the organic matter content of the soil. An iterative procedure was used to identify the wavelengths that correlated best with organic matter content. No absorption peak due to soil organic matter was found in the infrared and visible regions of the spectrum scanned. The optimal wavelengths for predicting percent organic matter content are 0.6236 and 0.5644 µm and the model is of the form: Organic matter content = K × d log(r⁻¹₀.₆₂₃₆)/dλ₀.₆₂₃₄ / d log(r⁻¹₀.₅₈₄₄)/dλ₀.₅₈₄₄
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