A high seed yield and associated attributes of dry matter production achieved by recent Japanese soybean cultivars

Figures & data

Table 1. Dates (month/day and DAS) and CISR values at the R1, R5, and R6 stages for the Hatsusayaka and Sachiyutaka soybean cultivars grown at normal (D12) and dense (D18) densities in 2014 and 2015.

Cultivar	Year	Density	R1	R5	R6
			Date (DAS)	CISR (MJ m^−2)	Date (DAS)	CISR (MJ m^−2)	Date (DAS)	CISR (MJ m^−2)
Hatsusayaka	2014	D12	8/20 (33)	99 ± 2	9/18 (62)	510 ± 5	9/22 (66)	555 ± 5
		D18	8/20 (33)	134 ± 2	9/18 (62)	558 ± 3	9/22 (66)	604 ± 3
	2015	D12	8/18 (36)	167 ± 9	9/9 (58)	421 ± 11	9/24 (71)	619 ± 11
		D18	8/18 (36)	207 ± 5	9/ 9 (58)	463 ± 5	9/24 (71)	662 ± 5
ANOVA	Year (Y)		−	***	−	***	−	***
	Density (D)		−	***	−	***	−	***
	Y×D		−	ns	−	ns	−	ns
Sachiyutaka	2015	D12	8/17 (35)	150 ± 8	9/9 (58)	416 ± 11	9/24 (71)	613 ± 11
		D18	8/17 (35)	195 ± 5	9/9 (58)	467 ± 8	9/24 (71)	665 ± 8
t-test			−	***	−	**	−	**

Notes: Mean ± S.E. (n = 6). ns, not significant.

* p < .05

** p < .01

*** p < .001.

Figure 1. Changes in (a) mean temperature, (b) daily total solar radiation, and (c) precipitation at 10-day intervals (i.e. an average of three times per month) to represent the early (E), middle (M), and late (L) parts of the month during the experimental periods in 2014 and 2015. Averages represent the 13-year mean from 2001 to 2013 at the meteorological station adjacent to the study site. Asterisks (*) indicate values outside of the 95% confidence interval for the 13-year mean (i.e. significantly higher or lower values).

Table 2. Yield, yield components, AGDM, harvest index, and lodging angle at maturity for the soybean cultivars Hatsusayaka and Sachiyutaka grown at normal (D12) and dense (D18) densities in 2014 and 2015.

Cultivar	Year	Density	Seed yield^a (g m^−2)	Seed No. (m^−2)	Fertile pod No. (m^−2)	Node No. (m^−2)	Branch No. (m^−2)	100 seeds weight^a (g)	AGDM (g m^−2)	Harvest index (%)	Lodging angle^b (°)
Hatsusayaka	2014	D12	381 ± 17	1108 ± 38	997 ± 33	402 ± 10	106 ± 4	34.3 ± .5	640 ± 33	57.3 ± 1.0	22.8 ± 1.5
		D18	432 ± 14	1286 ± 31	1096 ± 26	532 ± 11	141 ± 9	33.6 ± .7	706 ± 16	58.4 ± 1.0	24.3 ± 1.5
	2015	D12	486 ± 30	1448 ± 89	1048 ± 56	526 ± 18	124 ± 5	33.6 ± .3	793 ± 42	57.2 ± .9	10.5 ± .8
		D18	590 ± 56	1767 ± 155	1304 ± 123	680 ± 37	159 ± 10	33.3 ± .4	986 ± 86	56.0 ± 1.3	14.7 ± 1.3
ANOVA	Year (Y)		***	***	ns	***	*	ns	***	ns	***
	Density (D)		*	*	*	***	***	ns	*	ns	*
	Y × D		ns	ns	ns	ns	ns	ns	ns	ns	ns
Sachiyutaka	2015	D12	545 ± 29	1435 ± 69	915 ± 50	443 ± 19	110 ± 2	37.9 ± .5	810 ± 46	60.4 ± .9	12.3 ± 2.1
		D18	658 ± 53	1706 ± 133	1063 ± 86	588 ± 32	126 ± 6	38.5 ± .2	997 ± 75	58.9 ± .4	14.7 ± 3.2
t-test			ns	ns	***	**	*	ns	ns	ns	ns

Notes: Mean ± S.E. (n = 6). ns, not significant.

^a Seed yield and 100 seeds weight were adjusted 15% w/w moisture.

^b Lodging angle is the angle formed between main stem and vertical direction (Vertical = 0°).

* p < .05

** p < .01

*** p < .001.

Figure 2. Changes of (a, b) AGDM and (c, d) LAI for the soybean cultivars (H, Hatsusayaka; S, Sachiyutaka) at normal (D12) and dense (D18) densities in 2014 and 2015. Values are means ± S.E. (n = 6).

Table 3. Maximum AGDM, maximum LAI, CISR at the last destructive samples (82 DAS in 2014 and 87 DAS in 2015), RUE, and the date (DAS) and CISR values when FIPAR reached 80% and 90%.

Cultivar	Year	Density	Max. AGDM (g m^−2)	Max. LAI (m^2 m^−2)	CISR at last harvest (MJ m^−2)	RUE (g MJ^−1)	FIPAR at 80%	FIPAR at 90%
							DAS	CISR (MJ m^−2)	DAS	CISR (MJ m^−2)
Hatsusayaka	2014	D12	867 ± 36	4.3 ± .2	762.0 ± 6.1	1.21 ± .05	40.7 ± .6	177.0 ± 3.6	45.0 ± .6	222.0 ± 4.4
		D18	1012 ± 38	5.3 ± .3	812.9 ± 2.6	1.32 ± .05	38.7 ± .2	195.4 ± 3.7	42.3 ± .5	239.0 ± 5.2
	2015	D12	1168 ± 100	6.9 ± .2	844.8 ± 11.1	1.38 ± .13	35.5 ± .6	154.7 ± 6.8	38.5 ± 1.2	194.3 ± 11.4
		D18	1463 ± 100	8.5 ± .3	890.1 ± 5.7	1.68 ± .09	34.0 ± .4	176.3 ± 4.1	37.0 ± .6	215.8 ± 4.9
ANOVA	Year (Y)		***	***	***	***	***	***	***	***
	Density (D)		***	***	***	*	**	***	*	*
	Y × D		ns	ns	ns	ns	ns	ns	ns	ns
Sachiyutaka	2015	D12	1043 ± 57	5.7 ± .3	840.8 ± 11.2	1.23 ± .06	36.8 ± 1.1	173.1 ± 8.4	41.3 ± .8	229.6 ± 10.9
		D18	1331 ± 53	7.6 ± .6	893.2± 8.3	1.54 ± .09	34.7 ± .8	188.8 ± 5.3	38.3 ± 1.3	238.9 ± 12.6
t-test			***	*	**	*	ns	ns	ns	ns

Notes: Mean ± S.E. (n = 6). ns, not significant.

* p < .05

** p < .01

*** p < .001.

Figure 3. Changes in SLA of the soybean cultivars (a) Hatsusayaka and (b) Sachiyutaka grown at normal (D12) and dense (D18) densities in 2014 and 2015. Values are means ± S.E. (n = 6).

Figure 4. Changes in SPAD values of the soybean cultivars (a) Hatsusayaka and (b) Sachiyutaka grown at normal (D12) and dense (D18) densities in 2014 and 2015. Values are means ± S.E. (n = 6).

Figure 5. Changes of (a, b) CGR, (c, d) NAR, and (e, f) mLAI of the two soybean cultivars (H, Hatsusayaka; S, Sachiyutaka) at normal (D12) and dense (D18) densities in 2014 and 2015. Values are means ± S.E. (n = 6).

Figure 6. Linear regressions for the relationships between CGR and (a, c) NAR and (b d) mLAI before (a, b) and after (c, d) stage R3 for the two soybean cultivars (H, Hatsusayaka; S, Sachiyutaka) in 2014 and 2015. Linear regression equations are presented only for the following statistically significant relationships. Coefficients of determination (R²) are (a) Hatsusayaka 2015: R² = .968 (p < .05), (b) Hatsusayaka 2014: R² = .994 (p < .001), Hatsusayaka 2015: R² = 1.000 (p < .001), Sachiyutaka 2015: R² = .998 (p < .001), (c) Hatsusayaka 2014: R² = .671 (p < .05), Hatsusayaka 2015: R² = .920 (p < .001), Sachiyutaka 2015: R² = .889 (p < .001). (d) No significant relationships.

Figure 7. Linear regression relationships between AGDM and CISR for the two soybean cultivars for (a) Hatsusayaka and (b) Sachiyutaka grown at normal (D12) and dense (D18) densities in 2014 and 2015. Values are means ± S.E. (n = 6). Equations and coefficients of determination (R²) are (a) Hatsusayaka: D12 in 2014: y = −34.8 + 1.207x, R² = .978 (p < .001), D18 in 2014: y = −35.3 + 1.295x, R² = .995 (p < .001), D12 in 2015: y = −15.4 + 1.381x, R² = .993 (p < .001), D18 in 2015: y = −66.6 + 1.678x, R² = .990 (p < .001), (b) Sachiyutaka: D12 in 2015: y = −3.7 + 1.229x, R² = .986 (p < .001), D18 in 2015: y = −33.5 + 1.541x, R² = .995 (p < .001).

Table 4. Daily total solar radiation during the experiments in 2014 and 2015, and the 13-year means (2001–2013) at the meteorological station adjacent to the study site.

Month	Daily total solar radiation (MJ m^−2 d^−1)
	2014	2015	13-yr mean
July	19.0	16.5	19.7
August	12.9	17.9	20.9
September	16.0	13.5	16.2
October	12.1	14.7	12.7
E−H^a	1429	1623	−

^a Total of daily total solar radiation (MJ m⁻²) from emergence to the day before harvest in 2014 and 2015.