Deep rooting development and growth in upland rice NERICA induced by subsurface irrigation

Figures & data

Figure 1. Irrigation treatment applied at different soil depths with a syringe.

Table 1. Root morphology in upland rice irrigated at different soil depths.

		RSA	RL	RD	BN	RL/BN	NRN	RL at deep	Ratio of RL
	Treatment	(cm^2 plant^−1)	(cm plant^−1)	(mm)	(plant^−1)	(mm branch^−1)	(plant^−1)	layer^a (cm plant^−1)	at deep layer^b(%)
Exp. 1	0 cm	165 c (100)	2323 c (100)	0.23 a (100)	26700 c (100)	0.87 a (100)	6.0 a (100)	143 b (100)	5.6 b
	5 cm	167 c (101)	2399 bc (103)	0.22 a (98)	29477 bc (110)	0.82 a (94)	8.0 a (133)	138 b (96)	5.4 b
	10 cm	211 b (127)	3032 b (130)	0.22 a (98)	37002 ab (139)	0.82 a (94)	5.3 a (89)	441 b (308)	14.0 b
	20 cm	278 a (168)	3799 a (164)	0.23 a (103)	41131 a (154)	0.92 a (106)	5.5 a (92)	1710 a (1196)	45.0 a
		***	***	n.s.	**	n.s.	n.s.	**	**
Exp. 2	0 cm	227 a (100)	2988 a (100)	0.24 a (100)	33206 a (100)	0.91 a (100)	5.3 a (100)	576 ab (100)	18.4 c
	5 cm	221 a (97)	2895 a (97)	0.24 a (100)	34264 a (103)	0.85 a (94)	5.7 a (108)	152 b (26)	5.2 c
	10 cm	258 a (114)	3810 a (127)	0.21 a (89)	44273 a (133)	0.85 a (94)	4.3 a (83)	1560 a (271)	39.4 b
	20 cm	177 a (82)	2602 a (85)	0.22 a (96)	27280 a (81)	0.97 a (107)	4.0 a (76)	1551 a (269)	59.5 a
		n.s.	n.s.	n.s.	n.s.	n.s.	n.s.	*	***
Exp. 3	0 cm	106 b (100)	1583 b (100)	0.21 a (100)	19161 b (100)	0.83 a (100)	2.8 ab (100)	341 c (100)	22.7 b
	5 cm	231 a (217)	3451 a (218)	0.21 ab (99)	43588 a (227)	0.79 a (96)	4.2 a (150)	1006 bc (295)	28.5 b
	10 cm	218 a (205)	3375 a (213)	0.21 ab (96)	41189 a (215)	0.82 a (96)	2.6 ab (93)	1642 b (481)	48.4 ab
	20 cm	256 a (240)	4240 a (268)	0.19 b (90)	49299 a (257)	0.87 a (104)	1.4 b (50)	2779 a (814)	65.2 a
		***	***	*	***	n.s.	**	***	***
Treatment	0 cm	162 B (100)	2243 B (100)	0.23 A (100)	25802 B (100)	0.87 AB (100)	4.5 AB (100)	352 C (100)	16.1 C
	5 cm	211 AB (130)	3012 AB (134)	0.22 A (98)	37197 A (144)	0.82 B (94)	5.6 A (124)	536 C (152)	15.9 C
	10 cm	227 A (140)	3400 A (152)	0.21 A (93)	40888 A (158)	0.83 B (96)	3.8 B (84)	1292 B (367)	36.6 B
	20 cm	237 A (146)	3661 A (163)	0.21 A (91)	41060 A (159)	0.91 A (105)	3.0 B (66)	2197 A (623)	59.5 A
Exp.	1	196 A (100)	2765 A (100)	0.23 A (100)	32375 A (100)	0.85 AB (100)	6.3 A (100)	477 B (100)	14.2 C
	2	221 A (113)	3067 A (111)	0.23 A (102)	34637 A (107)	0.90 A (105)	4.8 B (78)	930 B (195)	29.7 B
	3	203 A (103)	3162 A (114)	0.21 B (91)	38309 A (118)	0.83 B (97)	2.8 C (44)	1442 A (302)	41.2 A
Treatment		***	***	n.s.	***	***	***	***	***
Exp.		n.s.	n.s.	***	n.s.	**	***	***	***
Treatment × Exp.		***	***	n.s.	**	n.s.	n.s.	*	n.s.

*, ** and *** indicate 5%, 1% and 0.1% levels of significance, respectively. n.s. indicates no significance. Same alphabetical letters indicate no significance at the 5% level between treatments and between Exps. Lowercase letters indicate Tukey’s multiple test with a one-way analysis of treatments in each Exp. Capital letters indicate Tukey’s multiple test with a two-way analysis of treatments and Exps. Values in parentheses indicate the percentage of the 0-cm treatment and Exp. 1. ^aDeeper layer than 15 cm from the ground surface. ^bThe percentage of root length at the deep layer to total length. The statistical analysis was conducted after arcsine transformation. Exp., experiment; RSA, root surface area; RL, root length; RD, root diameter; BN, branch number; NRN, nodal root number.

Figure 2. Correlation between the numbers of root branches and root lengths in upland rice. *** indicates 0.1% level of significance.

Table 2. Root morphology analyzed at every 5 cm of soil depth in upland rice irrigated at different soil depths.

Depth	Treatment	RSA(cm^2)	RL(cm)	RD(mm)	BN	RL/BN(mm branch^-1)
0-5 cm	0 cm	29.0 a (100)	441 a (100)	0.21 a (100)	5459 a (100)	0.082 b (100)
	5 cm	25.9 ab (89)	415 a (94)	0.20 ab (96)	5169 ab (95)	0.084 b (102)
	10 cm	18.0 bc (62)	312 ab (71)	0.18 b (87)	3642 bc (67)	0.087 ab (106)
	20 cm	13.5 c (47)	214 b (49)	0.20 ab (94)	2225 c (41)	0.098 a (119)
		***	***	**	***	**
5-10 cm	0 cm	53.2 b (100)	795 b (100)	0.21 a (100)	9667 b (100)	0.083 b (100)
	5 cm	73.9 a (139)	1105 a (139)	0.21 a (101)	14243 a (147)	0.078 b (94)
	10 cm	43.3 bc (81)	741 b (93)	0.19 b (88)	9034 b (93)	0.083 b (99)
	20 cm	28.4 c (53)	470 c (59)	0.19 ab (92)	4991 c (52)	0.095 a (114)
		***	***	**	***	***
10-15 cm	0 cm	53.3 b (100)	710 b (100)	0.24 a (100)	7787 b (100)	0.095 a (100)
	5 cm	72.6 a (136)	963 ab (136)	0.25 a (103)	11363 ab (146)	0.090 ab (94)
	10 cm	75.4 a (141)	1138 a (160)	0.21 b (86)	13957 a (179)	0.082 b (86)
	20 cm	49.8 b (93)	819 b (115)	0.19 b (80)	9447 b (121)	0.088 ab (92)
		***	***	***	***	**
15-20 cm	0 cm	24.4 b (100)	280 b (100)	0.31 a (100)	2737 b (100)	0.161 a (100)
	5 cm	29.2 b (120)	375 b (134)	0.29 a (95)	4274 b (156)	0.112 a (70)
	10 cm	69.2 a (284)	930 a (331)	0.26 a (85)	10862 a (397)	0.097 a (60)
	20 cm	58.5 a (240)	914 a (326)	0.21 b (68)	10336 a (378)	0.092 a (57)
		***	***	***	***	n.s.
20-25 cm^a	0 cm	8.8 b (100)	119 b (100)	0.27 a (100)	939 b (100)	0.138 a (100)
	10 cm	23.0 b (263)	284 b (239)	0.31 a (112)	3340 b (356)	0.117 ab (85)
	20 cm	87.5 a (997)	1142 a (960)	0.26 a (95)	12383 a (1319)	0.099 b (72)
		***	***	n.s.	***	**

** and *** indicate 1% and 0.1% levels of significance, respectively. n.s. indicates no significance. Same alphabetical letters indicate no significance at the 5% level between treatments at the same depth. ANOVA and Tukey’s multiple test were conducted using a two-way analysis of treatments and Exps. Values in parentheses indicate the percentage of the 0-cm treatment. ^aThe 5-cm treatment was excluded from the statistical analysis at the depth of 20–25 cm because roots did not reach that depth in Exp. 2. RSA, root surface area; RL, root length; RD, root diameter; BN, branch number.

Table 3. Growing traits in upland rice irrigated at different soil depths.

		Plant length	Stem number	Leaf age	SDW	RDW	SDW/RDW
	Treatment	(mm)	(No. plant^−1)		(g plant^−1)	(g plant^−1)	ratio
Exp. 1	0 cm	384 a (100)	2.0 a (100)	5.5 c (100)	0.24 b (100)	0.30 a (100)	0.81 a
	5 cm	389 a (101)	2.7 a (133)	5.6 bc (102)	0.30 ab (127)	0.40 a (136)	0.75 a
	10 cm	396 a (103)	3.0 a (150)	5.7 ab (105)	0.37 a (157)	0.44 a (149)	0.85 a
	20 cm	389 a (101)	3.0 a (150)	6.0 a (109)	0.37 a (157)	0.64 a (216)	0.59 a
		n.s.	n.s.	**	**	n.s.	n.s.
Exp. 2	0 cm	403 b (100)	2.3 a (100)	6.0 a (100)	0.26 a (100)	0.35 a (100)	0.73 a
	5 cm	429 ab (107)	2.0 a (89)	6.0 a (101)	0.26 a (100)	0.36 a (102)	0.72 a
	10 cm	454 ab (113)	2.3 a (104)	6.1 a (103)	0.31 a (121)	0.41 a (118)	0.75 a
	20 cm	476 a (118)	2.3 a (104)	6.2 a (104)	0.22 a (83)	0.18 a (50)	1.23 a
		*	n.s.	n.s.	n.s.	n.s.	n.s.
Exp. 3	0 cm	244 c (100)	1.4 a (100)	4.9 c (100)	0.14 b (100)	0.17 c (100)	0.83 a
	5 cm	296 b (122)	2.2 a (157)	5.7 b (117)	0.26 a (183)	0.42 a (246)	0.61 a
	10 cm	322 ab (132)	2.2 a (157)	6.0 a (123)	0.27 a (194)	0.31 ab (179)	0.89 a
	20 cm	342 a (140)	1.8 a (129)	6.0 a (123)	0.26 a (185)	0.26 bc (150)	1.02 a
		***	***	***	***	***	n.s.
Treatment	0 cm	336 C (100)	1.8 B (100)	5.4 C (100)	0.21 B (100)	0.27 A (100)	0.78 A
	5 cm	358 B (107)	2.3 AB (123)	5.7 B (107)	0.27 A (130)	0.40 A (150)	0.68 A
	10 cm	378 AB (113)	2.5 A (133)	5.9 AB (110)	0.31 A (150)	0.37 A (141)	0.84 A
	20 cm	392 A (117)	2.2 AB (119)	6.0 A (112)	0.27 A (130)	0.31 A (116)	0.88 A
Exp.	1	389 B (100)	2.6 A (100)	5.6 B (100)	0.31 A (100)	0.42 A (100)	0.75 A
	2	437 A (112)	2.2 AB (86)	6.1 A (107)	0.26 B (84)	0.33 B (79)	0.80 A
	3	301 C (77)	1.9 B (74)	5.6 B (100)	0.23 B (75)	0.29 B (69)	0.81 A
Treatment		***	*	***	***	n.s.	n.s.
Exp.		***	**	***	***	**	n.s.
Treatment × Exp.		n.s.	n.s.	***	*	**	n.s.

*, ** and *** indicate 5%, 1% and 0.1% levels of significance, respectively. n.s. indicates no significance. Same alphabetical letters indicate no significance at the 5% level between treatments and between Exps. Lowercase letters indicate Tukey’s multiple test with a one-way analysis of treatments in each Exp. Capital letters indicate Tukey’s multiple test with a two-way analysis of treatments and Exps. Values in parentheses indicate the percentage of the 0-cm treatment and Exp. 1. Exp., experiment; SDW, shoot dry weight; RDW, root dry weight.

Figure 3. Images of root systems in upland rice irrigated at different soil depths (Exp. 3).