C and N dynamics of a range of biogas slurries as a function of application rate and soil texture: a laboratory experiment |
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Authors: | Anja Sänger Daniel Geisseler |
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Institution: | 1. Department of Environmental Chemistry, University of Kassel, Witzenhausen, Germany;2. Department of Technology Assessment and Substance Cycles, Leibniz Institute for Agricultural Engineering Potsdam-Bornim, Potsdam, Germany |
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Abstract: | Digestates vary in composition and studies regarding their impact on C and N dynamics in soils are scarce. The objective was to analyse the C and N dynamics of digestates originating from various substrates applied to a sandy Cambisol and a silty Anthrosol. In three laboratory experiments (4–6 weeks), the effects of digestate properties, N rate and water content were tested. Averaged over both soils, 21% of the C supplied was emitted as CO2. Potential NH3 emissions during the first week ranged between 6% and 12% of NH4+ present in the digestates. The emission factors in the sandy Cambisol were on average 1.2 and 2 times higher for CO2 and potential NH3, respectively, compared to the silty Anthrosol. Similarly, net nitrogen mineralization in the sandy Cambisol was approximately twice the N mineralized in the silty Anthrosol. Net nitrification was not influenced by soil texture or different digestates, but increased with increasing application rates and had highest values at 75% of water holding capacity. Our results indicate that the type of substrate input for anaerobic digestion influences the properties of the digestate and therefore the dynamics of C and N. However, soil texture can affect these dynamics markedly. |
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Keywords: | CO2 NH3 volatilization nitrification N mineralization soil texture |
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