Hydrophobicity of the organic matter in arable soils

A large number (92) of arable soils with widely differing textures and organic C contents have been investigated by diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) in order to establish relationships between the aliphatic CH IR signal area (3000-2800 cm−1) and chemical, microbiological and textural properties of the soils studied. Significant correlations were found between the investigated variables. The results indicate that the soil texture influences the composition of the soil organic matter and implicitly the amount of microbial biomass. Thus, the organic matter of sandy soils contains more alkyl C and less carbohydrates and proteins compared with clayey ones, in other words it is more hydrophobic. The aliphatic CH-to-Corg ratio, which in the present study varied between 3.5–21.7, could serve to characterize the degree of hydrophobicity of the soil organic matter. A high ratio indicates a greater hydrophobicity.