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Temporal evolution of biochar's impact on soil nitrogen processes – a 15N tracing study |
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| Authors: | Victoria Nelissen Tobias Rütting Dries Huygens Greet Ruysschaert Pascal Boeckx |
| Institution: | 1. Department of Earth Sciences, University of Gothenburg, Box 460, Gothenburg, 405 30 Sweden;2. Isotope Bioscience Laboratory – ISOFYS, Faculty of Bioscience Engineering, Ghent University, Coupure 653, Gent, 9000 Belgium
Institute of Agricultural Engineering and Soil Science, Faculty of Agricultural Sciences, Universidad Austral de Chile, Valdivia, Chile Instituto Multidisciplinario de Biología Vegetal - IMBIV, Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina;3. Institute for Agricultural and Fisheries Research (ILVO), Plant Sciences Unit, Burgemeester Van Gansberghelaan 109, Merelbeke, 9820 Belgium;4. Isotope Bioscience Laboratory – ISOFYS, Faculty of Bioscience Engineering, Ghent University, Coupure 653, Gent, 9000 Belgium |
| Abstract: | Biochar addition to soils has been proposed as a means to increase soil fertility and carbon sequestration. However, its effect on soil nitrogen (N) cycling and N availability is poorly understood. To gain better insight into the temporal variability of the impact of biochar on gross soil N dynamics, two 15N tracing experiments, in combination with numerical data analysis, were conducted with soil from a biochar field trial, 1 day and 1 year after application of a woody biochar type. The results showed accelerated soil N cycling immediately following biochar addition, with increased gross N mineralization (+34%), nitrification (+13%) and ammonium (NH4+) and nitrate (NO3?) immobilization rates (+4500% and +511%, respectively). One year after biochar application, the biochar acted as an inert substance with respect to N cycling. In the short term, biochar's labile C fraction and a pH increase can explain stimulated microbial activity, while in the longer term, when the labile C fraction has been mineralized and the pH effect has faded, the accelerating effect of biochar on N cycling ceases. In conclusion, biochar accelerates soil N transformations in the short-term through stimulating soil microbial activity, thereby increasing N bio-availability. This effect is, however, temporary. |
| Keywords: | 15N Biochar field trial gross transformation immobilization mineralization nitrogen tracing model |