Table 1. Total N₂O emissions from 15 agricultural soils un-amended (control) or mixed with 2% biochar (dry weight basis) under denitrification conditions (90% WFPS and 30°C). Soils were spiked with KNO₃ (¹⁵N 99% enrichment), which allowed the determination of the total N denitrified (N₂ + N₂O) and the ratio N₂O/(N₂ + N₂O) by the ¹⁵N gas-flux method.

	Total N2O produced after 12 days of incubation					Fluxes of N2 and N2O when the difference between biochar and control N2O fluxes was maximum**
	Total cumulative N2O (mg N2O-N kg−1 soil)		Total cumulative N2O respect to initial NO3− in soil (%)			N2 (μmol kg−1 soil h−1)		N2O (μmol kg−1 soil h−1)		N2O/(N2 + N2O)
Soil	Control	Biochar	Control	Biochar	Mitigation (%)	Control	Biochar	Control	Biochar	Control	Biochar
Elba	120	108	91.4	82.5	10	2.75	3.03	17.39	17.99	0.864	0.856
Lins	0.9	1.3	1.4	1.9	−38	0.06	0.06	2.26	0.44	0.972	0.850
Arkport	2.9	1.0	4.3	1.4	67	15.77	4.82	0.54	0.09	0.053	0.038
Lentiscosa	2.1	1.5	2.6	1.8	31	3.41	23.73	4.45	2.34	0.550	0.159
Tioga	10.3	4.0	17.2	6.6	61	0.12	0.14	1.43	0.38	0.820	0.651
Howard	17.0	10.3	23.2	14.1	39	1.23	2.08	7.46	9.39	0.793	0.766
Secanos	12.3	3.1	8.5	2.1	75	5.23	0.76	3.64	0.61	0.443	0.394
Cabezo	6.5	0.7	8.8	1.0	89	10.95	4.29	1.74	0.67	0.295	0.142
Hudson A	0.4	0.3	0.7	0.6	18	0.22	0.22	0.36	0.48	0.607	0.291
Madalin	15.1	1.9	14.7	1.8	88	0.58	0.97	3.64	0.17	0.795	0.130
Niagara	23.9	6.6	18.6	5.1	72	0.41	1.06	18.53	9.10	0.971	0.854
Hudson B	9.0	3.8	15.2	6.4	58	3.59	4.04	7.28	4.61	0.643	0.511
Costa	30.6	6.1	2.7	0.5	80	7.79	14.25	5.67	2.36	0.458	0.179
Coronela	69.8	7.0	12.9	1.3	90	14.49	2.26	9.99	1.47	0.468	0.244
Guarapuava	3.3	0.4	4.2	0.5	89	0.17	0.09	1.63	0.14	0.782	0.447

Values are the mean of 4 replicates.