Effects of different application timings of methane fermentation digested liquid to paddy plots on soil nitrogen and rice yield

Figures & data

Figure 1. Experimental paddy plots. DBP, days before ponding.

Table 1. Applications of digested liquid and cultivation practices

	2008	2009	2010
Basal application	6, 12, 17 May	6, 10, 16 May	8, 15, 22 May
DBP (d)	0, 5, 11	0, 6, 10	1, 8, 15
Method	Injecting	Spreading	Spreading
Ponding & puddling	17 May (0)	16 May (0)	23 May (0)
Transplanting	25 May (8)	24 May (8)	27 May (4)
Additional application	18 Jul. (62)	22–23 Jul. (67–68)	29 Jul. (67)
Harvest	17 & 22 Sep. (123 & 128)	20 & 21 Sep. (127 & 128)	18 & 19 Sep. (118 & 119)
Sampling date for PFS	17 Jul. (61)	20 Jul. (65)	17 Jul. (55)
Sampling date for EES	12 Aug. (87)	11 Aug. (87)	13 Aug. (82)
DBP, days before ponding; PFS, panicle formation stage; EES, ear emergence stage. The numbers in parentheses indicate days after ponding (DAP).

Table 2. Components of methane fermentation liquid for application (mg NL⁻¹)

		T-N	DON	-N	-N	-N
2008	BA	2357 ± 154	413 ± 7	1313 ± 61	6.1 ± 2.7	N.D.
2009	BA	3911 ± 246	460 ± 70	2052 ± 89	17.0 ± 21.1	N.D.
	AA	3660 ± 482	568 ± 152	2190 ± 494	7.4 ± 2.9	N.D.
2010	BA	3476 ± 146	1535 ± 251	1211 ± 207	2.0 ± 1.4	1.6 ± 0.2
	AA	2738 ± 93	252 ± 34	1792 ± 53	N.D.	N.D.
BA, basal application; AA, additional application; T-N, total nitrogen; DON, dissolved organic nitrogen; N.D., non-detectable.
Values indicate average ± standard deviation.

Figure 2. Climate changes for crop seasons over 3 years. DAP, days after ponding; TP, transplanting; PFS, panicle formation stage; AA, additional application; EES, ear emergence stage.

Figure 3. Temporal changes in nitrogen (N) concentrations in soil before transplanting. The symbols and error bars indicate the average and standard deviation of sub-plots (2 sampling points), respectively. DAP; days after ponding; DBP, days before ponding; TP, transplanting; DON, dissolved organic nitrogen. *Denotes significant differences in each sub-plot.

Figure 4. Temporal changes in nitrogen (N) concentrations in soil from transplanting to additional application. The symbols and error bars indicate the average and standard deviation of sub-plots (2 sampling points), respectively. DAP, days after ponding; DBP, days before ponding; TP, transplanting; AA, additional application; PFS, panicle formation stage; DON, dissolved organic nitrogen. *Denotes significant differences in each sub-plot.

Figure 5. Temporal changes in nitrogen (N) concentrations in soil from additional application to harvest. The symbols and error bars indicate the average and standard deviation of sub-plots (2 sampling points), respectively. DAP, days after ponding; DBP, days before ponding; AA, additional application; EES, ear emergence stage; DON, dissolved organic nitrogen. *Denotes significant differences in each sub-plot.

Figure 6. The average values (2 sampling points) of rice (Oryza sativa L.) yield, taste, dry weight, nitrogen (N) concentration, and N content at sub-plots. PFS, panicle formation stage; EES, ear emergence stage; DBP, days before ponding. The error bar indicates standard deviation. The numbers in the figure denote DBP. *Denotes the significance level P < 0.05; **denotes P < 0.01. The black bars indicate that at the same plot in the same year, the values for shorter DBP are smaller than those for longer DBP. The gray bars indicate the reverse, i.e., values for shorter DBP are greater than those for longer DBP.

Figure 7. The correlations between the dissolved organic nitrogen (DON) concentration and rice yield in 2008 at days after ponding (DAP) = 0, 61, and 66.

Table 3. Correlation coefficients between rice variables and soil dissolved organic nitrogen (DON) concentrations in soil on all investigation dates

			DAP	0	2	4	7	12	26	39	54	61	66	73	93	109
DON	2008		Dry weight	0.29	−0.06	−0.31	−0.08	0.30	0.20	0.34	−0.42
		PFS	N concentration	−0.47	0.00	0.53	0.09	0.12	−0.57	−0.07	0.08
			N content	0.08	−0.07	−0.11	−0.07	0.48	0.00	0.45	−0.54
			Dry weight	−0.06	0.16	0.16	0.04	0.67	−0.22	0.67	−0.61	−0.13	−0.17	−0.47
		EES	N concentration	0.80	0.65	−0.45	0.87	0.57	0.11	0.32	−0.35	0.32	0.85	0.48
			N content	0.49	0.58	−0.19	0.63	0.87	−0.08	0.71	−0.68	0.09	0.45	0.00
			Rice taste	−0.70	−0.27	0.60	−0.24	−0.01	−0.65	−0.03	0.11	−0.44	−0.50	−0.39	−0.46	−0.37
			Yield	0.85	0.34	−0.19	0.49	0.13	−0.09	0.18	−0.14	0.73	0.67	0.55	0.22	0.09
			DAP	0	11	18	25	32	39	46	53	61	67	72	87	95	107
DON	2009		Dry weight	−0.11	0.30	0.42	0.49	0.21	−0.12	0.12	−0.49	−0.23
		PFS	N concentration	−0.16	0.01	−0.07	0.01	0.34	0.39	0.06	0.43	0.49
			N content	−0.31	0.40	0.51	0.59	0.45	0.05	0.16	−0.37	0.01
			Dry weight	−0.19	0.30	0.37	0.15	−0.16	−0.45	−0.03	−0.61	−0.38	−0.28	−0.44
		EES	N concentration	0.36	−0.09	−0.11	0.27	0.40	0.46	0.00	0.29	0.70	−0.38	−0.03
			N content	0.15	0.10	0.16	0.31	0.20	0.03	−0.08	−0.27	0.31	−0.56	−0.40
			Rice taste	−0.32	−0.02	0.06	−0.44	−0.51	−0.53	−0.18	−0.45	−0.66	0.22	0.07	0.15	−0.48	−0.59
			Yield	0.27	0.18	−0.01	0.15	0.32	0.40	0.34	0.51	0.40	−0.18	0.21	0.01	0.14	0.41
			DAP	2	6	9	16	23	30	37	44	51	59	66	68	73	82	88	96	103	117
DON	2010		Dry weight	0.09	0.37	0.35	0.30	0.03	0.19	0.28	0.27	−0.23
		PFS	N concentration	0.24	0.03	0.00	−0.05	0.13	0.18	−0.02	−0.04	0.15
			N content	0.33	0.47	0.43	0.31	0.16	0.38	0.29	0.25	−0.12
			Dry weight	−0.04	−0.27	−0.22	−0.04	−0.13	0.10	−0.06	0.15	0.03	0.00	−0.31	0.34	−0.17
		EES	N concentration	0.33	0.16	0.13	0.12	0.39	0.41	0.38	0.23	0.35	0.28	−0.38	−0.02	−0.27
			N content	0.23	−0.05	−0.04	0.04	0.23	0.35	0.25	0.24	0.29	0.24	−0.45	0.15	−0.31
			Rice taste	−0.02	0.19	0.12	−0.06	−0.04	0.08	0.19	0.38	0.14	−0.02	−0.18	0.04	−0.10	0.15	0.02	0.10	0.03	0.19
			Yield	0.08	0.21	0.11	−0.07	−0.37	−0.17	−0.23	−0.29	−0.36	−0.40	0.27	−0.41	0.22	−0.01	0.49	0.16	0.40	0.38
DON, dissolved organic nitrogen; DAP, days after ponding; PFS, panicle formation stage; EES, ear emergence stage. Significant correlations are highlighted in bold. The numbers of sampling points are 10, 12 and 16 in 2008, 2009 and 2010, respectively.

Table 4. Correlation coefficients between rice variables and soil ammonium-nitrogen (-N) concentrations in soil on all investigation dates

			DAP	0	2	4	7	12	26	39	54	61	66	73	93	109
	2008		Dry weight	−0.13	−0.08	0.11	−0.09	−0.41	−0.43	0.00	0.36
		PFS	N concentration	0.23	0.01	0.55	−0.03	0.66	0.79	0.49	−0.53
			N content	−0.04	−0.09	0.45	−0.09	−0.13	−0.13	0.28	0.14
			Dry weight	−0.09	0.11	0.72	0.04	0.19	0.15	0.67	−0.36	−0.32	0.39	0.92
		EES	N concentration	0.55	0.71	0.27	0.53	−0.60	0.04	0.51	0.12	0.00	−0.10	0.08
			N content	0.33	0.57	0.70	0.39	−0.25	0.16	0.83	−0.18	−0.19	0.24	0.71
			Rice taste	0.01	−0.35	0.62	−0.38	0.73	0.65	0.34	−0.56	0.08	0.46	0.40	0.08	0.27
			Yield	0.14	0.46	0.05	0.17	−0.83	−0.26	0.25	0.28	−0.37	−0.05	−0.04	−0.47	−0.45
			DAP	0	11	18	25	32	39	46	53	61	67	72	87	95	107
	2009		Dry weight	0.39	0.29	0.45	0.31	0.20	0.10	0.15	−0.43	0.07
		PFS	N concentration	0.01	0.13	0.00	0.03	0.15	0.30	0.25	0.42	0.21
			N content	0.57	0.44	0.61	0.40	0.40	0.36	0.35	−0.29	0.20
			Dry bweight	0.58	0.10	0.52	0.34	0.51	0.17	0.10	−0.41	−0.16	0.11	0.05
		EES	N concentration	−0.29	0.13	0.06	0.28	0.34	0.62	0.09	0.32	0.41	0.66	−0.27
			N content	0.20	0.14	0.42	0.49	0.69	0.68	0.10	−0.08	0.25	0.69	−0.17
			Rice taste	0.26	−0.30	−0.14	−0.41	−0.35	−0.52	−0.35	−0.52	−0.35	−0.41	0.49	−0.24	−0.68	−0.48
			Yield	−0.20	0.23	0.10	0.19	0.20	0.37	0.28	0.37	0.01	0.28	−0.16	0.38	0.32	0.28
			DAP	2	6	9	16	23	30	37	44	51	59	66	68	73	82	828	96	103	117
	2010		Dry weight	0.21	0.32	0.29	0.23	0.07	0.26	0.00	0.02	−0.36
		PFS	N concentration	0.12	0.38	0.44	0.29	0.52	0.40	0.48	0.61	0.76
			N content	0.39	0.78	0.80	0.58	0.64	0.72	0.48	0.66	0.37
			Dry weight	−0.19	−0.18	−0.17	−0.21	−0.26	−0.13	−0.15	−0.11	−0.23	0.21	−0.01	0.34	−0.29
		EES	N concentration	0.13	0.35	0.35	0.26	0.36	0.26	0.11	0.26	0.35	0.23	−0.45	−0.12	0.30
			N content	−0.02	0.17	0.17	0.07	0.13	0.12	−0.02	0.15	0.16	0.31	−0.36	0.07	0.07
			Rice taste	−0.12	0.19	0.22	−0.20	0.00	0.07	−0.08	−0.06	−0.15	−0.04	−0.27	0.20	−0.12	0−0.17	0.07	0.11	−0.10	0.14
			Yield	0.03	0.11	0.00	0.05	−0.05	0.09	0.15	−0.06	−0.31	−0.21	0.36	−0.25	−0.40	−0.10	−0.35	−0.23	−0.02	0.60
DAP, days after ponding; PFS, panicle formation stage; EES, ear emergence stage. Significant correlations are highlighted in bold. The numbers of sampling points are 10, 12 and 16 in 2008, 2009 and 2010, respectively.