3 years ago

Offsetting global warming-induced elevated greenhouse gas emissions from an arable soil by biochar application

Offsetting global warming-induced elevated greenhouse gas emissions from an arable soil by biochar application
Sven Marhan, Chris Bamminger, Christian Poll
Global warming will likely enhance greenhouse gas (GHG) emissions from soils. Due to its slow decomposability, biochar is widely recognized as effective in long-term soil carbon (C) sequestration and in mitigation of soil GHG emissions. In a long-term soil warming experiment (+2.5 °C, since July 2008) we studied the effect of applying high-temperature Miscanthus biochar (0, 30 t/ha, since August 2013) on GHG emissions and their global warming potential (GWP) during 2 years in a temperate agroecosystem. Crop growth, physical and chemical soil properties, temperature sensitivity of soil respiration (Rs), and metabolic quotient (qCO2) were investigated to yield further information about single effects of soil warming and biochar as well as on their interactions. Soil warming increased total CO2 emissions by 28% over 2 years. The effect of warming on soil respiration did not level off as has often been observed in less intensively managed ecosystems. However, the temperature sensitivity of soil respiration was not affected by warming. Overall, biochar had no effect on most of the measured parameters, suggesting its high degradation stability and its low influence on microbial C cycling even under elevated soil temperatures. In contrast, biochar × warming interactions led to higher total N2O emissions, possibly due to accelerated N-cycling at elevated soil temperature and to biochar-induced changes in soil properties and environmental conditions. Methane uptake was not affected by soil warming or biochar. The incorporation of biochar-C into soil was estimated to offset warming-induced elevated GHG emissions for 25 years. Our results highlight the suitability of biochar for C sequestration in cultivated temperate agricultural soil under a future elevated temperature. However, the increased N2O emissions under warming limit the GHG mitigation potential of biochar. In a long-term soil warming experiment, we found elevated soil temperature to enhance the Global Warming Potential (GWP) of soil greenhouse gas emissions over 2 years, while biochar had no effect. Although biochar did not reduce GHG emissions from warmed soil, its sequestration was estimated to offset global warming-induced elevated GHG emissions of more than two decades. However, the increased N2O emissions from warmed biochar-amended soil limits the GHG mitigation potential of biochar.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/gcb.13871

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