Fig. 4. Attenuated total reflectance Fourier transform infrared spectroscopy spectra of, from top to bottom, native Betsele soil, Betsele soil + 14 mmol dm^–3 phosphate, Betsele soil + 28 mmol dm^–3 phosphate, native Flakastugan soil, Flakastugan soil + 14 mmol dm^–3 phosphate, and Flakastugan soil + 28 mmol dm^–3 phosphate. All spectra are plotted on the same ordinate scale in absorbance units.