Fig. 5. Difference attenuated total reflectance Fourier transform infrared spectroscopy spectra obtained by subtracting the spectrum of the corresponding native soil from the spectrum (a) Betsele soil + 14 mmol dm^–3 phosphate, (b) Betsele soil + 28 mmol dm^–3 phosphate, (c) Flakastugan soil + 14 mmol dm^–3 phosphate, and (d) Flakastugan soil + 28 mmol dm^–3 phosphate. All spectra are plotted on the same ordinate scale in absorbance units.