Wheat straw and its biochar differently affect soil properties and field-based greenhouse gas emission in a Chernozemic soil

A 2-year field study was conducted to compare the effect of wheat straw, its biochar, and wheat straw plus biochar addition on soil fluxes of CO2, CH4, and N2O during the growing season, and soil properties and crop yield in a Black Chernozemic soil planted to barley (Hordeum vulgare L.) in central Alberta, Canada. The objective was to assess the benefit of applying biochar instead of its feedstock, wheat straw, in improving environmental sustainability. Biochar addition did not affect soil CH4 oxidation, but decreased CO2 and N2O emissions as compared with both wheat straw applied alone and wheat straw and biochar applied together in 2010 and 2011 (p < 0.001), and resulted in a lower global warming potential, indicating that the biochar was effective in mitigating greenhouse gas (GHG) emission from the agricultural soil, as a result of biochar suppressing soil microbial activity and reducing soil N availability. Biochar application reduced N2O emission over 2 years, indicating its longer-term impact. Biochar application alone increased barley yield by 9.9 to 20.4% as compared to the other three treatments, thus reducing yield-scaled greenhouse gas emission intensity by 27.2 to 50.9% (p = 0.013 for the control and p < 0.001 for both wheat straw-amended treatments), with an average reduction of 3.43 t CO2-eq t(-1) grain. The application of both wheat straw and its biochar reduced the temperature sensitivity of soil CO2 emission (Q(10), p < 0.001), but the application of wheat straw or its biochar alone did not affect Q(10), indicating that biochar application reduces the sensitivity to temperature changes of the decomposition of the new organic matter added to the soil. We conclude that (1) the application of wheat straw-derived biochar was preferred to raw wheat straw in mitigating GHG emission and (2) biochar can be an effective management strategy for properly handling crop residues in sustainable agriculture.