N2O and N2 losses from simulated injection of biogas digestate depend mainly on soil texture, moisture and temperature
Sebastian Rainer Fiedler1, Jürgen Augustin2, Nicole Wrage-Mönnig1, Gerald Jurasinski1, Bertram Gusovius2, and Stephan Glatzel1,a1Faculty of Agricultural and Environmental Sciences, University of Rostock, Rostock, 18059, Germany 2Institute for Landscape Biogeochemistry, Leibniz Centre for Agriculture Landscape Research (ZALF) e.V., Müncheberg, 15374, Germany anow at: Department of Geography and Regional Research, University of Vienna, Vienna, 1010, Austria
Received: 09 Feb 2017 – Accepted for review: 26 Feb 2017 – Discussion started: 28 Feb 2017
Abstract. Biogas digestate (BD) is increasingly used as organic fertiliser, but has a high potential for NH3 losses. Its proposed injection into soils as a counter-measure has been suggested to promote the generation of N2O, leading to a potential trade-off. Furthermore, the effect on N2 losses after injection of BD into soil has not yet been evaluated. We performed a simulated BD injection experiment in a helium-oxygen atmosphere to examine the influence of soil substrate (loamy sand, clayey silt), water-filled pore space (WFPS; 35, 55, 75 %), temperature (2° C, 15° C) and application rate (0, 160, 320 kg N ha−1) as a proxy for row spacing of injection on the emissions of N2O, N2, and CO2. To determine the potential capacity for these gaseous losses, we incubated under anaerobic conditions by purging with helium for the last 24 h of incubation. N2O and N2 emissions as well as the N2 / (N2O + N2) ratio depended on soil type and increased with WFPS and temperature, indicating a crucial role of soil gas diffusivity for the formation of these gases in agricultural soils. However, the emissions did not increase with the application rate of BD, i.e. a broader spacing of injection slits, probably due to an inhibitory effect of the high NH4+ content of BD. Our results suggest that the risk of N2O and N2 losses even after injection of relatively large amounts of BD seems to be small for dry to wet sandy soils and acceptable when regarding simultaneously reduced NH3 emissions for dry silty soils.
Fiedler, S. R., Augustin, J., Wrage-Mönnig, N., Jurasinski, G., Gusovius, B., and Glatzel, S.: N2O and N2 losses from simulated injection of biogas digestate depend mainly on soil texture, moisture and temperature, SOIL Discuss., doi:10.5194/soil-2017-6, in review, 2017.