Effects of charcoal addition on N₂O emissions from soil resulting from rewetting air-dried soil in short-term laboratory experiments

Abstract

Laboratory experiments were conducted to examine the effect of charcoal addition on N₂O emissions resulting from rewetting of air-dried soil. Rewetting the soil at 73% and 83% of the water-filled pore space (WFPS) caused a N₂O emission peak 6 h after the rewetting, and the cumulative N₂O emissions throughout the 120-h incubation period were 11 ± 1 and 13 ± 1 mg N m⁻², respectively. However, rewetting at 64% WFPS did not cause detectable N₂O emissions (−0.016 ± 0.082 mg N m⁻²), suggesting a severe sensitivity to soil moisture. When the soils were rewetted at 73% and 78% WFPS, the addition of charcoal to soil at 10 wt% supressed the N₂O emissions by 89% . In contrast, the addition of the ash from the charcoal did not suppress the N₂O emissions from soil rewetted at 73% WFPS. The addition of charcoal also significantly stimulated the N₂O emissions from soil rewetted at 83% WFPS compared with the soil without charcoal addition (P < 0.01). Moreover, the addition of KCl and K₂SO₄ did not show a clear difference in the N₂O emission pattern, although Cl⁻ and SO²⁻ ₄, which were the major anions in the charcoal, had different effects on N₂O-reducing activity. These results indicate that the suppression of N₂O emissions by the addition of charcoal may not result in stimulation of the N₂O-reducing activity in the soil because of changes in soil chemical properties.

Key words:

• denitrification
• K fertilization
• liming
• N₂O-reducing activity
• rewetting effect

ACKNOWLEDGMENTS

The authors thank Dr Yuzo Kurokawa (Tokyo University of Agriculture and Technology) for providing soil samples and Mr Sumio Yamada (JFE Holdings) for providing the charcoal samples. The work described in this report was financially supported by a Sasakawa Scientific Research Grant from The Japan Science Society (16-315), the TUA&T 21 Century COE program (Evolution and Survival of Technology-based Civilization: Professor Masayuki Horio) and by the Japan Society for the Promotion of Science Research Fellowships for Young Scientists (17-6518).