Effects of charcoal addition on N_2O emissions from soil resulting from rewetting air-dried soil in short-term laboratory experiments(Environment)

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Laboratory experiments were conducted to examine the effect of charcoal addition on N_2O emissions resulting from rewetting of air-dried soil. Rewetting the soil at 73% and 83% of the water-filled pore space (WFPS) caused a N_2O emission peak 6h after the rewetting, and the cumulative N_2O emissions throughout the 120-h incubation period were 11±1 and 13±1mg N m^<-2> , respectively. However, rewetting at 64% WFPS did not cause detectable N_2O emissions (-0.016±0.082mg 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 10wt% supressed the N_2O emissions by 89%. In contrast, the addition of the ash from the charcoal did not suppress the N_2O emissions from soil rewetted at 73% WFPS. The addition of charcoal also significantly stimulated the N_2O emissions from soil rewetted at 83% WFPS compared with the soil without charcoal addition (P<0.01). Moreover, the addition of KCl and K_2SO_4 did not show a clear difference in the N_2O emission pattern, although Cl^- and SO^<2->_4, which were the major anions in the charcoal, had different effects on N_2O-reducing activity. These results indicate that the suppression of N_2O emissions by the addition of charcoal may not result in stimulation of the N_2O-reducing activity in the soil because of changes in soil chemical properties.