Time-lagged induction of N₂O emission and its trade-off with NO emission from a nitrogen fertilized Andisol

Figures & data

Figure 1  Experimental schedule.

Table 1 Net nitrification rates and supplemental fertilizer derived N2O emission from the soils during the first 180 h and 25-day incubation after adding (15NH4)2SO4 or K15NO3 fertilizer and incubating at 25°C and 60% water-filled pore space

Fertilizer	Sample	Net nitrification rate			N2O emission			Ratio of N2O to N added (%)
		First 180 h (mg N kg^−1)	180–612 h (mg N kg^−1)	First 180  h/total (%)	First 180 h (µg N kg^−1)	Total (µg N kg^−1)	First 180  h/total (%)
(^15NH4)2SO4	1	91.3	169	35.1	30.7 ± 3.8 a	99.3 ± 12.6 a	31	0.038
	2	86.3	174	33.2	27.4 ± 2.2 a	108 ± 2 a	25	0.041
	3	210	49.6	80.9	179 ± 14 b	190 ± 18 b	94	0.072
	4	250	10.0	96.1	190 ± 6 b	198 ± 6.61 b	96	0.075
K^15NO3	1	–	–	–	2.06 ± 0.04 a	3.17 ± 0.84 a	65	0.001
	2	–	–	–	10.1 ± 0.6 b	17.8 ± 1.20 b	57	0.007
	3	–	–	–	4.64 ± 2.37 a	7.98 ± 5.70 ab	58	0.003
	4	–	–	–	1.80 ± 0.68 a	7.40 ± 1.12 ab	24	0.008
Mean ± standard deviation (n = 3). Values within the same column followed by different letters are significantly different at P < 0.05.

Figure 2  (a) Total N2O emission from the soils during the 25-day incubation with and without supplemental N addition. CK represents the treatment without supplemental N addition. (b) Supplemental (15NH4)2SO4-derived N2O emission from the soils during the 25-day incubation. Error bars denote the standard deviation (n = 3).

Table 2 Total N2O and NO emissions from the soils with and without supplemental N addition during the 25-day incubation

Fertilizer	Sample	Total N2O emission (µg N kg^−1 soil)				Total NO emission (µg N kg^−1 soil)				Ratio of NO/N2O (B/A)
		N added (A)	Control	From N added	Ratio of N2O to N added (%)	N added (B)	Control	From N added	Ratio of NO to N added (%)
(^15NH4)2SO4	1	105 ± 16.6 a	6.28 ± 0.73 a	98.7	0.038	8540 ± 268 c	0	8540	3.29	81
	2	226 ± 4.42 b	106 ± 13.0 b	120	0.046	8525 ± 668 c	6167 ± 411	2358	0.91	38
	3	214 ± 14.7 b	12.8 ± 11.1 a	201	0.077	1563 ± 198 a	0	1563	0.64	7
	4	222 ± 6.49 b	2.67 ± 0.22 a	219	0.084	3575 ± 101 b	0	3575	1.38	16
K^15NO3	1	7.18 ± 2.73 a	6.28 ± 0.73 a	0.90	0	0	0	0	0	−
	2	106 ± 8.0 b	106 ± 13.0 b	0	0	6407 ± 718	6167 ± 411	340	0.13	60
	3	6.58 ± 3.86 a	12.8 ± 11.1 a	−6.22	−0.002	0	0	0	0	−
	4	8.74 ± 5.13 a	2.67 ± 0.22 a	6.07	0.002	0	0	0	0	−
Mean ± standard deviation (n = 3). Values within the same column followed by different letters are significantly different at P < 0.05.

Figure 3  Change in cumulative (15NH4)2SO4-derived N2O emission from the soils during the 25-day incubation after adding supplemental (15NH4)2SO4. Error bars denote the standard deviation (n = 3).

Figure 4  Nitric oxide emission from the soils during the 25-day incubation after adding supplemental (15NH4)2SO4. Error bars denote the standard deviation (n = 3).

Figure 5  Correlation between NO and N2O emission from the soils during the 25-day incubation after adding (15NH4)2SO4.

Figure 6  Changes in (15NH4)2SO4-derived and concentrations in the soils during the 25-day incubation. Error bars denote the standard deviation (n = 3).

Table 3 Reaction models and best-fit parameters obtained from the rates of nitrification after adding supplemental (15NH4)2SO4 to Andisols and incubating at 25°C and 60% water-filled pore space

Incubation period	Sample	Reaction equation	n	R ^2
25 days	1	NO^− 3−N = 0.456 t – 12.249	8	0.96**
	2	NO^− 3−N = 0.378 t – 7.904	8	0.98**
	3	NO^− 3−N = 69.369 Ln(t) – 175.42	8	0.93**
	4	NO^− 3−N = 67.945 Ln(t)  – 165.31	8	0.94**
First 180 h	3	NO^− 3−N = 1.144 t + 2.318	4	0.98*
	4	NO^− 3−N = 1.276 t + 1.325	4	0.99**
*P < 0.05;
**P < 0.01.