Signatures of aromatic carbons in the infrared absorption spectra of soils.

High fertility of the terra preta soils is often attributed to the high concentration of aromatic compounds found in these soils. Chemical characterization of two soil samples collected from different locations in Botswana has shown some similar properties with terra preta. Fourier Transform Infrared (FTIR) analysis revealed five common absorption bands between the soil samples and the aromatic compounds. The common bands were found to be due to the vibration of the benzene ring thus indicating traces of aromatic compounds in the soil samples. X-ray diffraction (XRD) revealed the existence of only two major nutrients which are magnesium and calcium in the studied samples. The soil pHs were found to be 6.8 for the ploughing field soil and 7.4 for backyard garden soil sample which are higher than the previously reported pH of terra preta which ranges from 5.0 to 5.4.