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Generic Prediction of Soil Organic Carbon in Alfisols Using Diffuse Reflectance Fourier-Transform Mid-Infrared Spectroscopy

Kamau-Rewe, Mercy, Rasche, Frank, Cobo, Juan Guillermo, Dercon, Gerd, Shepherd, Keith D., Cadisch, Georg
Soil Science Society of America journal 2011 v.75 no.6 pp. 2358-2360
Alfisols, Fourier transform infrared spectroscopy, heat, least squares, prediction, provenance, reflectance, soil organic carbon
Partial least squares regression (PLSR) analysis was used for the generic prediction of soil organic C (C(org)) content in Alfisols using diffuse reflectance Fourier-transform mid-infrared spectroscopy (DRIFT-MIRS). For prediction improvement, we tested the potential of C(org) removal by heating and spectral subtraction of mineralogic signals in DRIFT-MIRS spectra. Eighty-seven Alfisol samples (C(org) range 1–32 g kg−1) of contrasting geographic origin were heated (550°C) or left untreated (NT). Spectra from DRIFT-MIRS were recorded and spectral subtraction was performed by taking the difference between DRIFT-MIRS spectra of NT and heated soils. Prediction of C(org) by PLSR was acceptable for NT (R2 = 0.93; root mean square error of cross validation = 0.20; residual prediction deviation = 3.7) but was not improved by heating and spectral subtraction. Additional studies are recommended to substantiate the potential of PLSR-based, generic quantification of C(org) in unheated soils for soil groups other than Alfisols and to assess if heating is suited to advance generic prediction of C(org) across soil orders with widely different mineralogic signatures.