Effect of lime-nitrogen application on N₂O emission from an Andosol vegetable field

Figures & data

Figure 1. Temporal variations in (a) daily precipitation (bars) and soil temperature (line) at a depth of 5 cm, (b) water-filled pore space (WFPS), (c) nitrous oxide (N₂O) emission, (d) carbon dioxide (CO₂) emission, and (e) methane (CH₄) flux over the course of the field experiment in the chemical fertilizer (CF), application of all nitrogen (N) fertilizer as lime-nitrogen (LN100) treatment, application of 50% of N as lime-nitrogen and the remainder as CF (LN50) treatment, and CF with dicyandiamide (CFD) plots. Error bars represent standard deviation (n = 3).

Figure 2. Relationships between nitrous oxide (N₂O) emission and soil temperature at 5 cm depth in the chemical fertilizer (CF) treatment, application of all nitrogen (N) fertilizer as lime-nitrogen (LN100) treatment, application of 50% of N as lime-nitrogen and the remainder as CF (LN50) treatment, and CF with dicyandiamide (CFD) treatment plots.

Figure 3. Temporal variations in (a) pH, and in the contents of (b) cyanamide (H₂CN₂), (c) dicyandiamide (DCD), (d) ammonium-nitrogen (NH₄-N), (e) nitrite-nitrogen (NO₂-N), and (f) nitrate-nitrogen (NO₃-N), and in (g) ammonium oxidation activity in the topsoil layer (0 to 5 cm) over the course of the field experiment in the chemical fertilizer (CF) treatment, application of all nitrogen (N) fertilizer as lime-nitrogen (LN100) treatment, application of 50% of N as lime-nitrogen and the remainder as CF (LN50) treatment, and CF with DCD (CFD) treatment plots. Error bars represent standard deviation (n = 3). DW, dry weight.

Table 1 Pearson's correlation coefficients for the relationships between the nitrous oxide (N₂O) emission rate and soil environmental factors [pH, soil temperature at a depth of 5 cm (ST5), water-filled pore space (WFPS)] and the contents of ammonium-nitrogen (NH₄-N), nitrite-nitrogen (NO₂-N), nitrate-nitrogen (NO₃-N), cyanamide (H₂CN₂), and dicyandiamide (DCD) in each fertilized plot

	Pearson's correlation coefficient
	pH	ST5	WFPS	NH4-N	NO2-N	NO3-N	H2CN2	DCD
N2O emission
CF	0.11	0.51***	−0.08	0.50***	−0.22	0.42**	nd	nd
LN100	−0.18	0.40**	−0.27	0.24	−0.18	−0.11	0.47**	0.24
LN50	−0.03	0.44**	−0.22	0.47**	0.03	−0.13	0.66***	0.28
CFD	0.17	0.09	−0.14	−0.06	−0.21	−0.14	nd	0.23
**P < 0.01, ***P < 0.001.
nd indicates no data available because no cyanamide (H2CN2) was detected in the chemical fertilizer (CF) and CF with dicyandiamide (CFD) plots, and no dicyandiamide (DCD) was detected in the CF plot. LN100, application of all nitrogen (N) fertilizer as lime-nitrogen; LN50, application of 50% of N as lime-nitrogen and the remainder as CF.

Figure 4. Relationships between soil ammonium-nitrogen (NH₄-N) content and soil dicyandiamide (DCD) content in the application of all nitrogen (N) fertilizer as lime-nitrogen (LN100) treatment, application of 50% of N as lime-nitrogen and the remainder as chemical fertilizer (LN50) treatment, and chemical fertilizer with DCD (CFD) plots. DW, dry weight.

Table 2 Pearson's correlation coefficient between soil ammonium-nitrogen (NH₄-N), nitrite-nitrogen (NO₂-N), and nitrate-nitrogen (NO₃-N) contents and soil cyanamide (H₂CN₂) and dicyandiamide (DCD) contents

	Pearson's correlation coefficient
	H2CN2	DCD
NH4-N
CF	nd	nd
LN100	0.27	0.72***
LN50	0.50*	0.61***
CFD	nd	0.75***
NO2-N
CF	nd	nd
LN100	0.31*	0.04
LN50	0.40**	0.06
CFD	nd	0.50**
NO3-N
CF	nd	nd
LN100	−0.31*	0.06
LN50	−0.25	−0.05
CFD	nd	0.09
*P < 0.05, **P < 0.001, ***P < 0.001.
nd indicates no data available because no H2CN2 was detected in the chemical fertilizer (CF) and CF with DCD (CFD) plots, and no DCD was detected in the CF plot. LN100, application of all nitrogen (N) fertilizer as lime-nitrogen; LN50, application of 50% of N as lime-nitrogen and the remainder as CF.

Figure 5. Relationships between soil mineral nitrogen (N) content and the soil cyanamide (H₂CN₂) content during the restricted period in which H₂CN₂ was detected in the soil of the application of all N fertilizer as lime-nitrogen (LN100) treatment plot (a, b, c) and the application of 50% of N as lime-nitrogen and the remainder as chemical fertilizer (LN50) treatment plot (d, e, f). NH₄-N, ammonium-N; NO₂-N, nitrite-N; NO₃-N, nitrate-N; DW, dry weight.

Figure 6. Temporal variations in (a) nitrous oxide (N₂O) emission, (b) pH, and contents of (c) cyanamide (H₂CN₂), (d) dicyandiamide (DCD), (e) ammonium-nitrogen (NH₄-N), (f) nitrite-nitrogen (NO₂-N), and (g) nitrate-nitrogen (NO₃-N) in the soil during the incubation experiment in the chemical fertilizer (CF) and lime-nitrogen (LN) treatments. Error bars represent standard deviation (n = 3). DW, dry weight.