Effects of land-use type and nitrogen addition on nitrous oxide and carbon dioxide production potentials in Japanese Andosols

Figures & data

Figure 1 Changes in nitrous oxide (N₂O) and carbon dioxide (CO₂) production in response to three levels of nitrogen (N) addition. Bars indicate the standard error (n = 3). A, G and F indicate apple orchard soil, grassland soil and forest soil, respectively. N0, N30 and N150 indicate N addition levels of 0, 30 and 150 kg N ha^–1 yr^–1, respectively. Arrows indicate the time of solution addition. N₂O-N, nitrous oxide-nitrogen; CO₂-C, carbon dioxide-carbon.

Table 1 General linear model analysis of the effects of land use type and nitrogen (N) addition treatment on cumulative nitrous oxide (N₂O) and carbon dioxide (CO₂) production during 12 weeks of incubation (n = 3)

Variable	Degree of freedom	Cumulative N2O production (mg N2O-N kg^−1 d.s.)			Cumulative CO2 production (g CO2-C kg^−1 d.s.)
		Type III sum of squares	F value	P value	Type III sum of squares	F value	P value
Land use (L)	2	3.21	296.41	0.001	3.68	39.9	0.001
N addition (N)	2	0.19	17.84	0.001	0.14	1.51	0.248
L*N	4	0.07	3.09	0.042	0.54	2.93	0.050
Error	18	0.1			0.83

d.s., dry soil. N₂O-N, nitrous oxide-nitrogen; CO₂-C, carbon dioxide-carbon.

Figure 2 Cumulative nitrous oxide (N₂O) and carbon dioxide (CO₂) production by soils collected from areas subjected to different land uses during 12 weeks of incubation under three levels of nitrogen (N) addition. Bars indicate the standard error (n = 3). Different letters indicate significant differences at p < 0.05 as determined by Tukey’s highly significant difference (HSD) test. A, apple orchard soil; G, grassland soil; F, forest soil; N0, N30 and N150 indicate N addition levels of 0, 30 and 150 kg N ha^–1 yr^–1, respectively. N₂O-N, nitrous oxide-nitrogen; CO₂-C, carbon dioxide-carbon.

Table 2 Pearson correlation coefficients between cumulative gas productions [nitrous oxide (N₂O) or carbon dioxide (CO₂)] from the soils without nitrogen (N) addition and initial soil properties under the three land use types (n = 9)

Variable	pH	EC	TC	TN	C/N ratio	NO3^−-N	NH4^+-N	SOC	SN	MBC	MBN
N2O	−0.928^**	0.972^**	−0.890^**	0.188	0.548	0.988^**	0.993^**	0.598	0.936^**	0.728^*	0.030
CO2	−0.795^*	0.816^**	−0.787^**	−0.413	0.203	0.886^**	0.866^**	0.838^**	0.817^**	0.407	0.405

^*and ^**indicate significant effects at p < 0.05 and p < 0.01, respectively. EC, electrical conductivity; TC, total carbon; TN, total nitrogen; C, carbon; N, nitrogen; NO₃^–-N, nitrate-nitrogen; NH₄⁺-N, ammonium-nitrogen; SOC, soluble organic carbon; SN, soluble nitrogen; MBC, microbial biomass carbon; MBN, microbial biomass nitrogen.

Figure 3 Correlation between net nitrogen (N) mineralization rate and carbon dioxide (CO₂) and nitrous oxide (N₂O) production rates with three levels of N addition under three land uses. A, apple orchard soil; G, grassland soil; F, forest soil; N0, N30 and N150 indicate N addition levels of 0, 30 and 150 kg N ha^–1 yr^–1, respectively. N₂O-N, nitrous oxide-nitrogen; CO₂-C, carbon dioxide-carbon.

Table 3 Chemical and microbial properties of initial soils at the three experimental sites

Land use	Apple orchard	Grassland	Forest
pH (H2O)	4.8 ± 0.3^b	5.5 ± 0.4^a	5.4 ± 0.2^a
EC (m S m^−1)	16.2 ± 2.9^a	7.6 ± 0.9^b	6.1 ± 0.8^b
TC (g kg^−1 d.s.)	93 ±13^c	124 ± 16^a	113 ± 11^b
TN (g kg^−1 d.s.)	8.5 ± 1.2^b	10.6 ± 1.6^a	7.2 ± 0.7^c
C/N ratio	11.0 ± 0.3^c	11.8 ± 0.3^b	15.8 ± 0.2^a
NO3^−-N (mg kg^−1 d.s.)	15.1 ± 4.8^a	3.5 ± 0.0^b	4.2 ± 0.8^b
NH4^+-N (mg kg^−1 d.s.)	4.1 ± 0.7^a	0.7 ± 0.1^b	0.7 ± 0.2^b
SOC (mg kg^−1 d.s.)	358 ± 57^a	198 ± 42^b	354 ± 32^a
SN (mg kg^−1 d.s.)	21 ± 6^a	12 ± 3^b	10 ± 1^b
MBC (mg kg^−1 d.s.)	737 ± 149^b	930 ± 97^ab	990 ± 121^a
MBN (mg kg^−1 d.s.)	51 ± 16^a	47 ± 6^a	59 ± 17^a
MBC/MBN ratio	16 ± 1.9^b	19.7 ± 1.5^a	17.1 ± 1.1^b

Different letters in the same column indicate a significant difference among the three land use types as determined by Tukey’s highly significant difference (HSD) test (p < 0.05, n = 3). H₂O, water; d.s., dry soil; EC, electrical conductivity; TC, total carbon; TN, total nitrogen; C, carbon; N, nitrogen; NO₃⁻-N, nitrate nitrogen; NH₄⁺-N, ammonium nitrogen; SOC, soluble organic carbon; SN, soluble nitrogen; MBC, microbial biomass carbon; MBN, microbial biomass nitrogen.

Table 4 Nitrous oxide (N₂O) conversion factor according to soil inorganic nitrogen (N) under three land-use types

Variable	N0	N30		N150
	CF	CF	NCF	CF	NCF
Apple orchard	4.56 ± 0.48^b	3.39 ± 0.18^a	1.20 ± 0.07^a	1.76 ± 0.16^a	0.70 ± 0.19^a
Grassland	5.00 ± 0.11^b	1.79 ± 0.18^b	0.41 ± 0.19^b	0.77 ± 0.08^b	0.40 ± 0.07^b
Forest	5.61 ± 0.18^a	1.85 ± 0.12^b	–0.02 ± 0.11^c	0.63 ± 0.03^b	0.13 ± 0.04^b

Different letters in the same column indicate a significant difference among the three land-use types as determined by Tukey’s highly significant difference (HSD) test (p < 0.05, n = 3).N0, without nitrogen addition; N30, with 9.9 mg N kg^–1 d.s. 12 weeks^–1 (equivalent to 30 kg N ha^–1 yr^–1); N150, with 16.5 mg N kg^–1 d.s. 4 weeks^–1 (equivalent to 150 kg N ha^–1 yr^–1). CF, conversion factor is calculated by cumulative N₂O production/(SIN + N addition); NCF, net N fertilizer conversion factor is calculated by cumulative N₂O production of (N treat – N0)/N addition.

Figure 4 Regression analyses between cumulative nitrous oxide (N₂O) production and nitrogen (N) addition. A, G and F indicate apple orchard soil, grassland soil and forest soil, respectively. N₂O-N, nitrous oxide-nitrogen.