Combined effects of nitrogen deposition and biochar application on emissions of N₂O, CO₂ and NH₃ from agricultural and forest soils

Figures & data

Table 1 Characteristics of the two soils and biochar used in the experiments

Item	Agricultural soil	Forest soil	Biochar
Texture	Silt clay	Loam
sand, %	3.5	50.7
silt, %	67.9	36.3
clay, %	28.6	13.0
Total C, g kg^–1	11.6	40.1	467.0
Total N, g kg^–1	1.4	1.2	5.6
pH (1:2.5 H2O)	5.1	5.2	9.4
CEC, cmol kg^–1	31.2	27.1	24.1
Bulk density, g cm^–3	1.0	0.9
Surface area, m^2 g^–1			8.9
Ash content, %			20.8

C: carbon; N: nitrogen; CEC: cation exchange capacity.

Table 2 Two-way analysis of variance (ANOVA) for the effects of nitrogen (N) and biochar (BC) on nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions and ammonia (NH₃) volatilization during the entire sampling period

			N2O-N (kg ha^−1 yr^−1)			CO2-C (kg ha^−1 yr^−1)			NH3-N (kg ha^−1  yr^−1)
	Factors	df	SS	F value	P value	SS	F value	p value	SS	F value	p value
Agricultural soil	N	2	149.91	41.79	< 0.0001	16737	1.40	0.2850	10.76	31.89	< 0.0001
	BC	1	19.84	11.06	0.0060	60743	10.13	0.0079	0.89	5.29	0.0402
	N × BC	2	4.32	1.21	0.3333	122694	10.23	0.0025	0.14	0.41	0.674
	Model	5	174.64	19.48	< 0.0001	193595	6.46	0.0039	12.7	15.05	< 0.0001
	Error	12
Forest soil	N	2	420.08	200.63	< 0.0001	177746	3.25	0.0745	6.11	38.756	< 0.0001
	BC	1	30.74	29.36	0.0002	1671284	61.10	< 0.0001	2.02	25.65	0.0003
	N × BC	2	8.95	4.28	0.0396	88740	1.62	0.2379	0.87	5.49	0.0202
	Model	5	477.73	91.27	< 0.0001	1894164	13.85	< 0.0001	9.55	1.91	< 0.0001
	Error	12

C, carbon; SS: the sum of squares; F value: the ratio of mean squares of two independent samples; p value: the index of differences between the control group and the experimental group. If p < 0.05 and p < 0.001, significant differences exists between the control group and the experimental group.

Table 3 The cumulative nitrous oxide (N₂O), carbon dioxide (CO₂) and ammonia (NH₃) emissions from the agricultural and forest soils during the entire sampling period

Treatment^†		Agricultural soil (kg ha^−1 yr^−1)			Forest soil (kg ha^−^1 yr^−1)
N	BC	N2O-N	CO2-C	NH3-N	N2O-N	CO2-C	NH3-N
Treatment effect (n = 3)
N0		7.54 ± 1.101^cd‡	1060.73 ± 36.25^b	1.83 ± 0.08^d	4.15 ± 0.09^e	1971.72 ± 133.41^a	2.64 ± 0.29^d
N60		9.73 ± 2.622^bc	1204.96 ± 110.63^ab	2.55 ± 0.53^cd	11.13 ± 0.55^c	2297.42 ± 186.96^a	3.89 ± 0.26^ab
N120		15.40 ± 0.632^a	1287.78 ± 42.04^ab	3.75 ± 0.24^ab	17.49 ± 1.66^a	2219.82 ± 123.91^a	4.42 ± 0.26^a
N0	BC	6.15 ± 1.113^d	1349.58 ± 170.19^a	2.38 ± 0.26^cd	3.33 ± 0.70^e	1453.38 ± 152.42^b	2.29 ± 0.16^d
N60	BC	8.05 ± 0.651^cd	1204.88 ± 46.65^ab	3.10 ± 0.44^bc	6.91 ± 0.44^d	1471.06 ± 99.08^b	2.95 ± 0.52^cd
N120	BC	11.87 ± 0.291^b	1254.11 ± 113.37^ab	4.36 ± 0.44^a	14.15 ± 0.25^b	1519.23 ± 10.00^b	3.25 ± 0.49^bc
N effect (n = 6)
N0 mean		6.85 ± 1.11^b	1205.16 ± 103.22^a	2.11 ± 0.17^b	3.74 ± 0.40^c	1712.55 ± 142.92^a	2.46 ± 0.23^b
N60 mean		8.89 ± 1.64^b	1204.92 ± 78.64^a	2.82 ± 0.49^b	9.02 ± 0.50^b	1884.24 ± 143.02^a	3.42 ± 0.39^a
N120 mean		13.64 ± 0.46^a	1270.95 ± 77.71^a	4.05 ± 0.34^a	15.82 ± 0.96^a	1869.53 ± 66.96^a	3.84 ± 0.37^a
BC effect (n = 9)
without biochar		10.89 ± 1.45^a	1184.49 ± 62.97^a	2.71 ± 0.28^b	10.92 ± 0.77^a	2162.99 ± 148.09^a	3.65 ± 0.27^a
with biochar		8.69 ± 0.69^b	1269.52 ± 110.07^a	3.28 ± 0.38^a	8.13 ± 0.46^b	1481.22 ± 87.17^b	2.83 ± 0.39^b

N: ammonium nitrate (NH₄NO₃) solution; BC: biochar; ^†N0, N60 and N120 represent the nitrogen (N) amendment at 0, 60, 120 kg N ha⁻¹ yr⁻¹; ^‡mean ± standard deviations; superscript lowercase letters within the same column between treatments indicate differences according to Tukey’s multiple range test (p < 0.05).

Figure 1 Dynamics of nitrous oxide (N₂O) emission rates from the (a) agricultural and (b) forest soils, carbon dioxide (CO₂) emission rates from the (c) agricultural and (d) forest soils, and (e) water-filled pore space (WFPS; the mean of all the soil samplings) and air temperature during samplings throughout the six nitrogen (N) deposition events (cycles) A: agricultural soil, F: forest soil, N: ammonium nitrate (NH₄NO₃) solution, BC: biochar, BCN: biochar and NH₄NO₃ solution, the bars indicate the standard error of the mean [± standard error (SE)] for the three replicates of each treatment.

Figure 2 The cumulative ammonia (NH₃) emissions from the (a) agricultural and (b) forest soils with and without biochar addition during the six nitrogen (N) deposition events (cycles) A: agricultural soil, F: forest soil, N: ammonium nitrate (NH₄NO₃) solution, BC: biochar, BCN: biochar and NH₄NO₃ solution, C: every N deposition event, the bars indicate the standard error of the mean [± standard error (SE)] for the three replicates of each treatment for the sum of the six N deposition events.