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

Figures & data

Table 1 Selected physico-chemical properties of the air-dried soils examined in this study (oven-dry basis)

Abbreviation of soil name	Date of sampling	pH (H2O)	Total C	Total N	C/N ratio	WSOC	NO^− 3-N	Denitrifiers	Water content	MWHC	Bulk density	Specific gravity	Porosity
			(mg C g^−1)	(mg N g^−1)		(µg g^−1)		(log MPN g^−1)	(g H2O g^−1)		(g cm^−3)		(cm^3 cm^−3)
TG2004	Apr. 2004	6.0	69.6	5.62	12.4	155	45.8	6.5	0.15	1.21	0.58	2.05	0.72
TG2005	Mar. 2005	5.4	70.3	5.45	12.9	74	6.4	6.2	0.13	1.11	0.59	2.03	0.71
MPN, most probable number; MWHC, maximum water-holding capacity; WSOC, water soluble organic carbon.

Table 2 Selected physico-chemical properties of charcoal and its ash examined in this study

	pH (H2O)^†	LOI (%)	Water content (g H2O g^−1)	MWHC (g H2O g^−1)	Bulk density (g cm^−3)	Particle density (g cm^−3)	Anion content (µmol g^−1)^‡
							Cl^−	NO^− 3	SO^2− 4
Charcoal	9.3	38	0.14	1.38	0.50	1.64	510	0	9
Ash	11.6	–	0.03	–	0.46	–	1240	2	80
^†1:5 ratio.
^‡Air-dried material basis in Yanai et al. LOI, weight loss-on-ignition; MWHC, maximum water-holding capacity; –, not determined.

Figure 1  Effect of rewetting on N2O emissions from soil (TG2005). An air-dried soil sample was rewetted using distilled water at 64 (×), 73 (⧫) and 83% (▪) of the water-filled pore space (WFPS) and incubated at room temperature. The values shown are the mean ± standard deviation of three replicates. The cumulative N2O emissions during the 120-h incubation period at a rewetting level of 64, 73 and 83% WFPS were −0.016 ± 0.082, 11 ± 1 and 13 ± 1 mg N m−2 (equivalent to −0.003 ± 0.03, 2.3 ± 0.3 and 2.8 ± 0.4 µg N g−1soil), respectively.

Figure 2  Effect of charcoal addition on N2O emissions from soil (TG2004) rewetted at 78% of the water-filled pore space of the soil. The values shown are the mean ± standard deviation of three replicates. The cumulative N2O emissions during the 168-h incubation period for the non-added control and the 10 wt% charcoal addition were 105 ± 14 and 11.1 ± 2.4 mg N m−2 (equivalent to 19.9 ± 2.7 and 2.1 ± 0.5 µg N g−1 soil), respectively.

Table 3 Estimation of Cl− and load onto soil (TG2005) by the addition of charcoal, ash and K solution

Application rate or concentration		Added into soil (µmol g^−1 soil)		Concentration in soil solution (mmol L^−1) at
				73% WFPS		83% WFPS
		Cl^−	SO^2− 4	Cl^−	SO^2− 4	Cl^−	SO^2− 4
Charcoal	2 wt%	10	0.2	NA	NA	10	0.2
Charcoal	8.2 wt%	42	0.7	46	0.8	40	0.7
Ash	1.6 wt%	20	1.3	23	1.5	NA	NA
KCl	10 mmol L^−1	7.5	0	8.5	0	NA	NA
K2SO4	5 mmol L^−1	0	3.7	0	4.3	NA	NA
NA, not applicable with respect to the objectives of this study; WFPS, water-filled pore space.

Figure 3  Effect of liming by using charcoal and its ash on N2O emissions from soil (TG2005) rewetted at 73% of its water-filled pore space. The values shown are the mean ± standard deviation of three replicates. The cumulative N2O emissions during the 72-h incubation period for the non-added control, ash-amended soil and charcoal-amended soil were 4.1 ± 1.9, 4.3 ± 1.2 and 0.8 ± 0.7 mg N m−2 (equivalent to 0.9 ± 0.4, 1.0 ± 0.3 and 0.2 ± 0.2 µg N g−1soil), respectively.

Figure 4  Effect of charcoal addition on N2O emissions from soil (TG2005) rewetted at 83% of its water-filled pore space. The values shown are the mean ± standard deviation of three replicates. The cumulative N2O emissions during the 72-h incubation period for the non-added control and the 2 and 8.2 wt% charcoal additions were 6.8 ± 0.9, 10.0 ± 0.8 and 10.3 ± 0.6 mg N m−2 (equivalent to 1.5 ± 0.2, 2.2 ± 0.2 and 2.4 ± 0.1 µg N g−1soil), respectively.

Figure 5  Effect of Cl− and of K salts on N2O emissions from soil (TG2005) rewetted at 73% of its water-filled pore space. An air-dried soil sample was rewetted using distilled water (control) or a K solution and incubated at room temperature. The values shown are the mean ± standard deviation of three replicates. The cumulative N2O emissions during the 72-h incubation period for the non-added control, the 10 mmol L−1 KCl-added soil and the 5 mmol L−1 K2SO4 added soil were 2.9 ± 0.6, 5.3 ± 6.1 and 4.4 ± 1.5 mg N m−2 (equivalent to 0.6 ± 0.1, 1.2 ± 1.3 and 1.0 ± 0.3 µg N g−1 soil), respectively.

YanaiY HatanoR OkazakiM ToyotaK.Chemical factors affecting the N2O-reducing activity of denitrifying communities – Analysis of the C2H2inhibition-based N2O production curve of soil

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