Effects of application of lime nitrogen and dicyandiamide on nitrous oxide emissions from green tea fields

Figures & data

Table 1 Timing of fertilizer application and the kinds and amounts of nitrogen (N) fertilizers applied to each treatment plot

Date		N application rate	Type of fertilizer^† (kg-N ha^−1)
First year	Second year	(kg N ha^−1)	Control plots	LN plots	DCD plots
Sep. 13, 2010	Sep. 7, 2011	86	U:40, RC:18, FM:28	LN:40, RC:18, FM:28	DCD:8, U:32, RC:18, FM:28
Oct. 6, 2010	Sep. 26, 2011	86	U:40, RC:18, FM:28	LN:40, RC:18, FM:28	DCD:8, U:32, RC:18, FM:28
Feb. 25, 2011	Feb. 21, 2012	87	AS:31, RC:22, FM: 34	LN:31, RC:22, FM: 34	DCD:8, AS:23, RC:22, FM: 34
Mar. 11, 2011	Mar. 14, 2012	87	AS:31, RC:22, FM: 34	LN:31, RC:22, FM: 34	DCD:8, AS:23, RC:22, FM: 34
Apr. 7, 2011	Apr. 5, 2012	63	AS:63	AS:63	AS:63
May 26, 2011	May 23, 2012	36	CF:36	CF:36	CF:36
Jun. 10, 2011	Jun. 8, 2012	63	AS:63	AS:63	AS:63
Jul. 8, 2011	Jul. 5, 2012	36	CF:36	CF:36	CF:36
Total		544

LN, plot supplemented with lime nitrogen; DCD, plot supplemented with dicyandiamide. AS: ammonium sulfate, U: urea, RC: rapeseed oil cake, FM: fish meal, CF: chemical fertilizers except for AS and U.

Table 2 Cumulative nitrous oxide (N₂O) emissions from three treatment plots

				Control	LN	DCD
Year	Period	From	To	(kg N ha^−1)	(kgN ha^−1)	(kgN ha^−1)
1st	I	Sep. 4, 2010	Nov. 29, 2010	2.9 ± 0.5 a	0.4 ± 0.04 b	0.6 ± 0.03 b
1st	II	Nov. 30, 2010	Feb. 25, 2011	0.1 ± 0.02 a	0.1 ± 0.002 ab	0.2 ± 0.03 b
1st	III	Feb. 26, 2011	May 23, 2011	2.3 ± 0.2 a	0.8 ± 0.1 b	1.1 ± 0.1 b
1st	IV	May 24, 2011	Sep. 6, 2011	1.9 ± 0.7 a	1.2 ± 0.1 a	2.8 ± 0.9 a
1st	Total	Sep. 4, 2010	Sep. 6, 2011	7.1 ± 0.6 a	2.5 ± 0.04 b	4.7 ± 0.9 ab
2nd	I	Sep. 7, 2011	Nov. 30, 2011	1.7 ± 0.3 ab	0.7 ± 0.1 a	2.1 ± 0.3 b
2nd	II	Dec. 1, 2011	Feb. 21, 2012	0.04 ± 0.01 a	0.04 ± 0.01 a	0.1 ± 0.03 a
2nd	III	Feb. 22, 2012	May. 22, 2012	2.6 ± 0.5 a	1.2 ± 0.2 b	2.2 ± 0.1 ab
2nd	IV	May. 23, 2012	Sep. 7, 2012	2.7 ± 0.5 a	2.6 ± 0.4 a	7.5 ± 0.2 b
2nd	Total	Sep. 7, 2011	Sep. 7, 2012	7.1 ± 1.3 a	4.5 ± 0.2 a	12.0 ± 0.3 b
1st, 2nd	Mean			7.1 ± 0.9 a	3.5 ± 0.1 b	8.3 ± 0.6 a

LN, plot supplemented with lime nitrogen; DCD, plot supplemented with dicyandiamide. Mean ± standard error of the mean. Different letters within each line indicate significant differences between fertilizer treatment. p < 0.05 according to Tukey’s highly significant difference (HSD) test.

Figure 1 Time series data for N₂O flux from soil between canopy of tea plants and daily rainfall. Means of three replicates +standard error of means. LN, plot supplemented with lime nitrogen; DCD, plot supplemented with dicyandiamide. Dotted line shows timing of nitrogen fertilizer application. Gray background shows periods I and III.

Figure 2 Time series data for (a) daily rainfall and soil temperature at 10-cm depth between canopy of tea plants and (b) Water filled pore space (WFPS) and oxygen (O₂) concentration at 10-cm depth between canopy of tea plants. Dotted line shows timing of nitrogen fertilizer application.

Figure 3 Time series data for (a) ammonium-nitrogen (NH₄⁺-N) concentration in soil, (b) nitrate-nitrogen (NO₃--N) concentration in soil, (c) ratio of NH₄⁺-N to NO₃^–-N concentration in soil, (d) soil pH (H₂O), and (e) dicyandiamide (DCD) concentration in soil. Means of three replicates +standard error of means. LN, plot supplemented with lime nitrogen; DCD, plot supplemented with DCD. Dotted line shows timing of nitrogen fertilizer application. (-) means dimensionless.