Allanblackia - President Biya and wife visit ICRAF

Partial least squares regression (PLSR) analysis was used for the generic prediction of soil organic C (Corg) content in Alfisols using diffuse reflectance Fourier-transform mid-infrared spectroscopy (DRIFT-MIRS). For prediction improvement we tested the potential of Corg removal by heating and spectral subtraction of mineralogic signals in DRIFT-MIRS spectra. Eighty-seven Alfisol samples (Corg 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 Corg 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 Corg in unheated soils for soil groups other than Alfisols and to assess if heating is suited to advance generic prediction of Corg across soil orders with widely different mineralogic signatures.