Quantity of hydrophobic functional CH-groups – decisive for soil water repellency caused by digestate amendment
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Institute of Plant Nutrition and Soil Science, University of Kiel, Hermann-Rodewald 2, 24118 Kiel, Germany
Institute of Soil Landscape Research, Leibnitz Centre for Agricultural Landscape Research, Eberswalder 84, 15374 Müncheberg, Germany
Int. Agrophys. 2015, 29(2): 247-255
Anaerobic digestates are used as organic fertilizers; however, they are suspected to interfere negatively with soils. To investigate the relevance of the anaerobic digestates compo­sition on potential wettability and contact angle of the soil, we mixed in a laboratory experiment 30 m³ ha-1 of anaerobic digestates derived from mechanically pre-treated substrates from maizeand sugar beet with a homogenized Cambic Luvisol. Fourier trans-form infrared-spectra and diffuse reflectance infrared Fouriertransform-spectra of particle intact and finely ground soil-anaerobic digestates-mixtures were analyzed to determine the quantities of hydrophobic functional groups in the soil-anaero­bic digestates-mixtures that are used here as an indicator for the potential hydrophobicity. The anaerobic digestates application increased the amount of hydrophobic functional groups of the mix­tures and reduced the wettability of the soil. However, for intact particle samples an up to threefold higher amount of hydrophobic groups was found as compared to the finely ground ones, indicating a dilution effect of mechanical grinding on the effectivity of the organic matter that is presumably located as a coat­ing on mineral soil particles. For the particle intact samples, the intensity of hydrophobic functional groups bands denoting hydro­phobic brickstones in organic matter is indicative for the actual wettability of the soil-anaerobic digestates-mixtures
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