Effects of Root Growth of Deep and Shallow Rooting Rice Cultivars in Compacted Paddy Soils on Subsequent Rice Growth

doi:10.1016/j.rsci.2023.03.017

Abstract

Abstract:

Rice is often grown as multiple seasons in one year, alternating between flooded and upland systems. A major constraint, introduced from the flooded system, is a plough pan that may decrease rooting depth and productivity of follow-on upland rice. Roots penetrating the plough pan under flooded rice system can leave a legacy of weaker root growth pathways. Deeper rooting rice cultivars could have a bigger impact, but no direct evidence is available. To explore whether a deep rather than a shallow rooting rice cultivar grown in a flooded cropping cycle benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle, a simulated flooded paddy in greenhouse was planted with deep (Black Gora) and shallow (IR64) rooting cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland and planted rice cultivar BRRI Dhan 28. The overall root length density (RLD), root surface area, the numbers of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared with the shallow rooting rice genotype, the deep rooting rice genotype as ‘first season’ crop produced 19% greater RLD, 34% greater surface area and 29% more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28% greater RLD, 35% greater surface area and 43% more branching for the shallow rather than deep rooting genotype planted in the ‘first season’. The results suggested that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

Key words: plough pan, root growth, biopores, crop rotation, Oryza sativa, preceding crop, zero-tillage

Md. Dhin Islam, Adam H. Price, Paul D. Hallett. Effects of Root Growth of Deep and Shallow Rooting Rice Cultivars in Compacted Paddy Soils on Subsequent Rice Growth[J]. Rice Science, 2023, 30(5): 459-472.

Figures/Tables 10

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Genotype	Soil structure treatment	Tiller number	Leaf number	Plant height (cm)	Shoot fresh weight (g)	Shoot dry weight (g)
Black Gora	Hard plough pan	6.8 ± 0.6	25.0 ± 2.1	85.8 ± 3.1	23.00 ± 0.66	5.21 ± 0.11
	Soft plough pan	7.5 ± 0.3	27.5 ± 1.2	92.2 ± 4.0	23.00 ± 0.70	5.55 ± 0.17
	No plough pan	8.3 ± 0.5	30.2 ± 1.0	89.0 ± 1.7	22.70 ± 0.73	5.94 ± 0.18
IR64	Hard plough pan	6.8 ± 0.6	32.8 ± 3.6	58.0 ± 1.2	14.70 ± 1.20	4.02 ± 0.30
	Soft plough pan	7.8 ± 1.3	34.5 ± 2.4	61.8 ± 2.3	17.80 ± 0.69	4.68 ± 0.24
	No plough pan	9.0 ± 0.4	38.2 ± 0.6	60.2 ± 1.3	18.80 ± 0.55	4.84 ± 0.19
Analysis of variance
Genotype (G)		NS	19.89***	207.84***	81.20***	38.35***
Soil structure (SS)		NS	NS	NS	NS	0.29**
G × SS		NS	NS	NS	4.15*	NS

Genotype	Soil structure treatment	Tiller number	Leaf number	Plant height (cm)	Shoot fresh weight (g)	Shoot dry weight (g)
Black Gora	Hard plough pan	6.8 ± 0.6	25.0 ± 2.1	85.8 ± 3.1	23.00 ± 0.66	5.21 ± 0.11
	Soft plough pan	7.5 ± 0.3	27.5 ± 1.2	92.2 ± 4.0	23.00 ± 0.70	5.55 ± 0.17
	No plough pan	8.3 ± 0.5	30.2 ± 1.0	89.0 ± 1.7	22.70 ± 0.73	5.94 ± 0.18
IR64	Hard plough pan	6.8 ± 0.6	32.8 ± 3.6	58.0 ± 1.2	14.70 ± 1.20	4.02 ± 0.30
	Soft plough pan	7.8 ± 1.3	34.5 ± 2.4	61.8 ± 2.3	17.80 ± 0.69	4.68 ± 0.24
	No plough pan	9.0 ± 0.4	38.2 ± 0.6	60.2 ± 1.3	18.80 ± 0.55	4.84 ± 0.19
Analysis of variance
Genotype (G)		NS	19.89***	207.84***	81.20***	38.35***
Soil structure (SS)		NS	NS	NS	NS	0.29**
G × SS		NS	NS	NS	4.15*	NS

Flooded season genotype	Soil structure treatment	Plant height (cm)	Tiller number	Leaf number	Shoot fresh weight (g)	Shoot dry weight (g)
Black Gora (BG)	Hard plough pan	63.0 ± 0.9	11.8 ± 0.5	48.5 ± 3.4	15.93 ± 0.61	5.24 ± 0.48
	Soft plough pan	64.2 ± 0.5	11.8 ± 0.5	49.0 ± 1.2	16.84 ± 0.44	6.04 ± 0.32
	No plough pan	63.2 ± 0.5	12.5 ± 0.3	51.8 ± 0.9	16.49 ± 0.60	5.60 ± 0.14
IR64	Hard plough pan	62.2 ± 1.1	11.5 ± 0.3	47.5 ± 2.2	18.02 ± 0.56	5.34 ± 0.30
	Soft plough pan	62.5 ± 0.6	12.0 ± 0.0	48.8 ± 0.5	17.65 ± 0.86	5.73 ± 0.40
	No plough pan	64.5 ± 0.9	11.8 ± 0.5	48.2 ± 1.5	17.57 ± 0.71	6.16 ± 0.37
Without plant	Hard plough pan	62.2 ± 1.1	12.0 ± 0.9	49.2 ± 3.0	18.29 ± 0.48	5.46 ± 0.28
	Soft plough pan	66.3 ± 1.2	12.7 ± 0.3	51.3 ± 1.8	19.59 ± 0.62	6.65 ± 0.29
	No plough pan	65.2 ± 1.1	12.8 ± 0.5	49.2 ± 1.6	18.20 ± 0.94	5.80 ± 0.38
Analysis of variance
Flooded season genotype (G)		NS	NS	NS	8.00**	NS
Soil structure (SS)		NS	NS	NS	NS	NS
G × SS		NS	NS	NS	NS	NS
Preceding BG vs IR64		NS	NS	NS	7.18*	NS

Flooded season genotype	Soil structure treatment	Plant height (cm)	Tiller number	Leaf number	Shoot fresh weight (g)	Shoot dry weight (g)
Black Gora (BG)	Hard plough pan	63.0 ± 0.9	11.8 ± 0.5	48.5 ± 3.4	15.93 ± 0.61	5.24 ± 0.48
	Soft plough pan	64.2 ± 0.5	11.8 ± 0.5	49.0 ± 1.2	16.84 ± 0.44	6.04 ± 0.32
	No plough pan	63.2 ± 0.5	12.5 ± 0.3	51.8 ± 0.9	16.49 ± 0.60	5.60 ± 0.14
IR64	Hard plough pan	62.2 ± 1.1	11.5 ± 0.3	47.5 ± 2.2	18.02 ± 0.56	5.34 ± 0.30
	Soft plough pan	62.5 ± 0.6	12.0 ± 0.0	48.8 ± 0.5	17.65 ± 0.86	5.73 ± 0.40
	No plough pan	64.5 ± 0.9	11.8 ± 0.5	48.2 ± 1.5	17.57 ± 0.71	6.16 ± 0.37
Without plant	Hard plough pan	62.2 ± 1.1	12.0 ± 0.9	49.2 ± 3.0	18.29 ± 0.48	5.46 ± 0.28
	Soft plough pan	66.3 ± 1.2	12.7 ± 0.3	51.3 ± 1.8	19.59 ± 0.62	6.65 ± 0.29
	No plough pan	65.2 ± 1.1	12.8 ± 0.5	49.2 ± 1.6	18.20 ± 0.94	5.80 ± 0.38
Analysis of variance
Flooded season genotype (G)		NS	NS	NS	8.00**	NS
Soil structure (SS)		NS	NS	NS	NS	NS
G × SS		NS	NS	NS	NS	NS
Preceding BG vs IR64		NS	NS	NS	7.18*	NS

Soil layer	Root parameter	Flooded season treatment (F)	Soil structure (SS)	F × SS	Preceding Black Gora vs IR64
Total	Root length density (cm/cm³)	5.29*	NS	NS	NS
	Surface area (cm²)	11.25***	NS	NS	NS
	Diameter (mm)	47.48***	7.11**	6.07**	NS
	Volume (cm³)	14.20***	NS	2.98*	NS
	Root tip density (cm^-3)	4.82*	NS	NS	NS
	Number of branches per plant	7.16**	NS	NS	NS
Topsoil	Root length density (cm/cm³)	9.64***	NS	NS	13.48**
	Surface area (cm²)	7.65**	NS	NS	9.34**
	Diameter (mm)	27.58***	NS	3.34*	NS
	Volume (cm³)	10.62***	NS	2.96*	6.80*
	Root tip density (cm^-3)	6.14**	NS	NS	NS
	Number of branches per plant	10.70***	NS	NS	16.21***
Plough pan	Root length density (cm/cm³)	10.67***	27.04***	NS	NS
	Surface area (cm²)	12.85***	12.63***	NS	NS
	Diameter (mm)	5.37*	50.10***	3.61*	NS
	Volume (cm³)	13.12***	NS	NS	NS
	Root tip density (cm^-3)	36.45***	53.09***	NS	NS
	Number of branches per plant	10.51***	44.75***	NS	NS
	Root length density (cm/cm³)	14.09***	45.91***	NS	NS
Subsoil	Root length density (cm/cm³)	12.64***	NS	NS	4.53*
	Surface area (cm²)	22.96***	NS	NS	9.42**
	Diameter (mm)	33.01***	NS	NS	11.82**
	Volume (cm³)	29.29***	NS	NS	12.05**
	Root tip density (cm^-3)	9.36***	NS	NS	3.41*
	Number of branches per plant	19.08***	NS	NS	7.12*
The flooded season treatments are no plant, Black Gora and IR64. For analysis of variance, values reported are the F-values and asterisks indicate the level of significance. NS means non-significant. *, P < 0.001; , P < 0.01; *, P < 0.05.