Variation in the emission factor of N₂O derived from chemical nitrogen fertilizer and organic matter: A case study of onion fields in Mikasa, Hokkaido, Japan

Figures & data

Table 1 Chemical properties of the soil layers in Gray Lowland soil (GL) and Brown Lowland soil (BL)

Site	Horizon	Depth	pH(H2O)^†	CEC (cmolc kg^−1)	Sand (%)	Silt (%)	Clay (%)	C (%)	N (%)	C/N
GL	Ap1	0–10	5.8	25.5	12.1	51.2	36.7	3.21	0.28	11.5
	Ap2	10–33	5.2	24.6	11.3	50.9	37.8	3.51	0.28	12.7
	Bg	33–64	4.4	27.1	2.90	47.9	49.2	4.91	0.31	16.0
	C	64–100	4.7	33.1	6.10	56.3	37.6	7.66	0.44	17.4
BL	Ap1	0–15	5.2	24.6	6.00	57.4	36.6	2.17	0.19	11.3
	Ap2	15–35	5.2	24.1	5.50	58.7	35.8	2.06	0.18	11.5
	Bg	35–100+	4.2	20.8	12.6	61.6	25.8	1.36	0.14	9.82
^†Soil : distilled water ratio was 1:2.5 (GL) and 1:5 (BL).

Figure 1  Seasonal variation in N2O flux at the Gray Lowland soil (GL) and Brown Lowland soil (BL) sites. The arrows indicate the time of chemical fertilizer application (CF), organic fertilizer application (OF), root cutting (RC) and harvest and residue application (H). The four treatments were: FOP, chemical nitrogen fertilization and organic matter application, with plants; F, chemical nitrogen fertilization only, without plants; OP, organic matter application, with plants; C, no fertilization or organic matter, and no plants. Error bars indicate standard deviation.

Figure 2  Seasonal variation in N2O-N/NO-N at the Gray Lowland soil (GL) and Brown Lowland soil (BL) sites. See Fig. 1 for an explanation of the arrows and treatments.

Figure 3  Seasonal variation in air and soil temperatures and water-filled pore space (WFPS) at the Gray Lowland soil (GL) and Brown Lowland soil (BL) sites. See Fig. 1 for an explanation of the treatments.

Figure 4  Seasonal variation in soil concentration and soil concentration at the Gray Lowland soil (GL) and Brown Lowland soil (BL) sites. See Fig. 1 for an explanation of the arrows and treatments.

Table 2 Nitrogen application, N2O emission, EFF and EFO in Gray Lowland soil (GL) and Brown Lowland soil (BL)

Year	Site	Chemical N (kg N ha^−1 year^−1)	Residue N (kg N ha^−1 year^−1)	Organic N (kg N ha^−1 year^−1)	N2O emission				EFF (%)	EFO (%)
					FOP	F	OP	C
2000	GL	242	86.9	0	16.7	8.78	9.90	4.44	2.79	9.06
2003		242	81.0	0	7.71	5.72	3.24	2.01	1.84	2.45
2004		242	92.3	0	17.3	16.7	4.00	7.34	5.50	0.64
2005		237	117	0	7.19	13.3	4.06	12.1	1.32	–5.22
2005	BL	284	98.7	82.5	5.56	2.83	1.88	1.81	1.30	1.51
FOP, chemical nitrogen fertilization and organic matter application, with plants; F, chemical nitrogen fertilization only, without plants; OP, organic matter application, with plants; C, no fertilization or organic matter, no plants; EFF, emission factor of N2O associated with the application of chemical nitrogen fertilizer; EFO, emission factor of N2O associated with the application of organic nitrogen.

Figure 5  Relationship between N2O emission and mean temperature and precipitation at the Gray Lowland soil (GL) site. (a) Relationship between the 2-month N2O emission and mean annual air temperature in the chemical nitrogen fertilization and organic matter application, with plants (FOP) and the chemical nitrogen fertilization only, without plants (F) treatments from May to June, (b) relationship between the 2-month N2O emission and precipitation in the FOP and the organic matter application, with plants (OP) treatments from September to October.

Figure 6  Relationships between emission factors (EF) and climatic conditions. (a) Relationship between the emission factor of N2O associated with the application of chemical nitrogen fertilizer (EFF) and mean annual air temperature, (b) relationship between the emission factor of N2O associated with the application of organic nitrogen (EFO) and mean annual relative humidity. Regression analysis carried out only on the Gray Lowland soil (GL) data.

Figure 7  Estimated versus the measured N2O emissions in the chemical nitrogen fertilization and organic matter application, with plants (FOP) treatment. •, Gray Lowland soil (GL); ○: Brown Lowland soil (BL).