Die Bodenkultur - Journal for Land Management, Food and Environment
A. Voelkner, R.H. Ellerbrock, D. Holthusen, R. Horn:
Effects of anaerobic digestates on wetting properties of a sandy Podzol and a loamy Cambisol
Since the payment of subventions for the production of renewable energy an increase of biogas plants has been documented in the last years. The production of biogas generates digestates which are used as organic fertilizer. It is assumed that digestates can have negative impacts for soils. Therefore, the aim of the study was to investigate effects of the application of anaerobic maize and sugar beet digestates (equivalent to 30 m³ ha-1 and 90 m³ ha-1) on the wettability of a loamy Cambic Luvisol and a sandy Podzol. Analysis was done by exposing samples to a FT-IR spectrometer. The obtained FT-IR spectra were analysed for the existence of certain organic compounds possibly responsible for reduced wettability.The difference in soil organic matter composition in terms of C-H/C=O ratios could be used as an indicator for the potential wetting behavior of the soils. For both soils the application of 30 m³ ha-1 of both maize and sugar beet digestates decreases the wettability as compared to the untreated soils. However, an application of 90 m³ ha-1 of digestates decreases only the wettability of the loamy soil while that of the sandy soil samples increases. The loamy Cambisol contains more iron compared to the sandy Podzol which can connect the mineral particles with the organic molecules and reduces therefore its wettability. Overall, the soil texture has been identified to be the decisive factor controlling the impact of digestates.
Key words: Anaerobic digestates, wettability, functional groups, FT-IR- spectroscopy, soil texture.