The study examined the effects of System of Rice Intensification (SRI) practices compared to conventional flooded rice cultivation (TF) on rice plant physiology, morphology, and grain yield in India. SRI resulted in better root growth and activity, more tillers, larger and erect leaves, higher chlorophyll content and photosynthesis rates, and delayed senescence compared to TF. These physiological improvements led to larger panicles with more spikelets, better grain filling, and heavier grains under SRI, resulting in a 42% increase in grain yield over TF. The study concluded that SRI management practices help rice plants express their genetic yield potential through improved root-shoot interactions and plant morphology and physiology.

1. Amod K. Thakur, Sreelata Rath, Ashwani Kumar
Influence of System of Rice Intensification (SRI)
practices on grain yield and associated
physiological changes in rice plants compared to
conventional flooded rice
Directorate of Water Management (ICAR)
Bhubaneswar, Orissa -751023, India

2. Objective
To examine the extent to which
making certain changes in crop
management practices can alter
phenotypical characteristics and
induce physiological changes in
rice plants.
How SRI practices affect rice
plants’ morphology, their
physiology, and their implications
on crop performance?
DWM(ICAR),IndiaDWM(ICAR),India

3. Methodology
Location: Deras Research Farm, Orissa, India
Season: Dry (January-May) 2007 & 2008
Soil: Aeric Haplaquepts, sandy clay-loam in texture, pH 5.5.
Design: RCBD - five replicates
Plot sizes: 20 × 10 m2
Variety: Surendra
Crop management systems:
System of Rice Intensification (SRI) and
Traditional flooding (TF) with standard management practices
DWM(ICAR),IndiaDWM(ICAR),India

4. Management
practices SRI TF
Seedling age,
days
12 21
Plant spacing
and density
20 x 20 cm
One seedling /hill
20 x10 cm
Three
seedlings /hill
Weed control Three, Cono-
weeder; 10, 20 and
30 DAT
Manual, 10, 20
and 30 DAT
Water
management
AWD after 3 DAD
during vegetative
stage
Flooding with 5-6
cm depth of
water during the
vegetative stage.
Nutrient
management
Organic manure @ 5 t ha-1
Chemical fertilizers: 80 kg N ha-1
, 40 kg
P2
O5
ha-1
, 40 kg K2
O ha-1
DWM(ICAR),IndiaDWM(ICAR),India

5. Parameters studied
Root growth / Xylem exudation rate: Early-ripening stage
Number of leaves hill-1
/ Av. Leaf length and width / Leaf angle /
Leaf area index (LAI) / Specific leaf weight (SLW) / Canopy angle:
Flowering stage
Light interception by the canopy / Crop growth rate (CGR):
Vegetative stage
Chlorophyll content / Chlorophyll fluorescence (Fv/Fm and ΦPS
II) / Photosynthesis rate - flag leaf and fourth leaf (from top):
Flowering, Middle-ripening and Late-ripening stages
Tilering/ Harvest Index / Grain yield and yield-components
DWM(ICAR),IndiaDWM(ICAR),India

6. Results

7. RootGrowth
SRI- better root development -
deeper roots, more dry weight, root
volume, root length and root length
density
Parameters SRI TF LSD0.50
Root depth, cm 33.5 20.6 3.5
Root dry weight, g hill-1
12.3 5.8 1.3
Root dry weight, g m-2
306.9 291.8 NS
Root volume, ml hill-1
53.6 19.1 4.9
Root volume, ml m-2
1340.0 955.0 180.1
Root length, cm hill-1
9402.5 4111.9 712.4
Root length density, cm cm-3
2.7 1.2 0.2
DWM(ICAR),IndiaDWM(ICAR),India

8. RootActivity
Manage
ment
practice
Amount of
exudates per
hill (g hill-1
)
Amount of
exudates
per area
(g m-2
)
Rate per hill
(g hill-1
h-1
)
Rate per
area
(g m-2
h-1
)
SRI 7.61 190.25 0.32 7.93
TF 2.46 122.95 0.10 5.12
LSD.05
1.45 39.72 0.06 1.66
Amount of exudates- 209%
greater in SRI hills
Rate - 3 times faster in SRI hills
Thakur et al. (2010): Expl. Agric. 46: 77-98
DWM(ICAR),IndiaDWM(ICAR),India

9. TilleringunderSRI
The number of tillers per hill significantly
increased (2.5 times, up to 34 tillers) in SRI than TF
SRI plants were able to complete more number of
phyllochrons (10th
Phyllochron in SRI and 8th
phyllochron in TF)
0
5
10
15
20
25
30
35
12 21 30 40 50 60 70
Tillernumber/hill
Days after seed germination
DWM(ICAR),IndiaDWM(ICAR),India
Thakur et al. (2010): Expl. Agric. 46: 77-98

10. Phyllochrons
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
10th
11th
12th
New Tillers 1 0 0 1 1 2 3 5 8 12 20 31
Total tillers 1 1 1 2 3 5 8 13 21 33 53 84
Comparison between numbers of phyllochrons completed under SRI and TF
Manag
ement
practic
e
12 DAG 30 DAG 40 DAG 50 DAG 60 DAG 70 DAG
SRI Transplanted
< 4th
phyllochron
6th
Phyllochron
7– 8th
phyllochron
8-9th
phyllochron
9th
phyllochron 10th
Phyllochron
TF In
Nursery
Transplantin
g shock
6th
Phyllochron
7th
phyllochron
8th
phyllochron 8th
Phyllochron
DAG: Days after germination

11. CropGrowthRate
The increase in CGR in SRI crops was mainly due to
maintenance of leaf area (lower leaf senescence) -
Lower rate of leaf senescence might be due to
larger amounts of CYTOKININS (xylem exudates)
are transported from roots.
0
10
20
30
40
50
60
30-40 40-50 50-60 60-70
CGR(gm-2day-1)
Period (Days after germination)
DWM(ICAR),IndiaDWM(ICAR),India

12. Leafdevelopment
Management
practice
Leaf
number
(hill-1
)
Leaf
number
(m-2
)
Ave. leaf
length
(cm)
Ave. leaf
width
(cm)
LAI
SRI 79.8 1997.6 65.25 1.82 3.95
TF 35.6 1766.5 48.14 1.34 2.60
LSD.05
15.8 229.4 6.09 0.21 0.28
SRI hills - more than twice the
number of leaves compared to TF
hills
SRI leaves- longer as well as
wider than TF leaves
DWM(ICAR),IndiaDWM(ICAR),India

13. Canopystructure
&Leafangle
SRI: Greater Canopy angle -
Open-type canopy structure
TF: Closed-canopy structure
SRI leaves – more erect
Thakur et al. (2010): Expl. Agric. 46: 77-98
DWM(ICAR),IndiaDWM(ICAR),India

14. LightInterception
SRI: intercept more light without
shading
TF: In closed canopy lower leaves
experiences more shading.
0
20
40
60
80
100
12 25 30 40 50 60 70
LightInterception(%)
Days after seed germination
At PI Stage- Light
interception reached 89%
in SRI plots, while it was
only 78% in TF canopies,
this giving SRI plants a
15% advantage.
DWM(ICAR),IndiaDWM(ICAR),India

15. Changes in leaf chlorophyll content at
different growth stages in SRI and TF
FL: Flowering stage; MR: Middle-ripening stage; LR: Late-ripening stage
0
0.5
1
1.5
2
2.5
3
3.5
4
FL MR LR
Chlorophyllcontent(mgg-1FW)
Stages
Flag SRI
Flag TF
Fourth SRI
Fourth TF
% decrease
from FL-LR
SRI-Flag leaf 35.93
TF- Flag leaf 48.94
SRI-4th
leaf 39.44
TF- 4th
leaf 56.14
DWM(ICAR),IndiaDWM(ICAR),India

16. 0.3
0.4
0.5
0.6
0.7
0.8
0.9
FL MR LR
Fv/Fm
Stages
Flag SRI
Flag TF
Fourth SRI
Fourth TF
% decrease
from FL-LR
SRI-Flag leaf 22.77
TF- Flag leaf 31.81
SRI-4th
leaf 27.55
TF- 4th
leaf 31.88
Changes in chlorophyll fluorescence (Fv/Fm)
at different growth stages in SRI and TF
FL: Flowering stage; MR: Middle-ripening stage; LR: Late-ripening stage
DWM(ICAR),IndiaDWM(ICAR),India

17. 0.200
0.250
0.300
0.350
0.400
0.450
0.500
0.550
0.600
0.650
FL MR LR
ФPSII
Stages
Flag SRI
Flag TF
Fourth SRI
Fourth TF
% decrease
from FL-LR
SRI-Flag leaf 9.93
TF- Flag leaf 21.62
SRI-4th
leaf 15.31
TF- 4th
leaf 24.27
Changes in chlorophyll fluorescence (Φ PS II)
at different growth stages in SRI and TF
FL: Flowering stage; MR: Middle-ripening stage; LR: Late-ripening stage
DWM(ICAR),IndiaDWM(ICAR),India

18. 0
5
10
15
20
25
30
FL MR LR
Pn(µmolm-2s-1)
Stages
Flag SRI Flag TF
Fourth SRI Fourth TF
% decrease
from FL-LR
SRI-Flag leaf 43.20
TF- Flag leaf 51.09
SRI-4th
leaf 52.98
TF- 4th
leaf 59.02
Changes in photosynthesis rate at different
growth stages in SRI and TF
FL: Flowering stage; MR: Middle-ripening stage; LR: Late-ripening stage
DWM(ICAR),IndiaDWM(ICAR),India

19. Yield&yield-contributing
Characteristics
SRI - Longer panicles, more
number of grains in spike (40%),
higher 1000-grain weight and
more grain ripening percent than
the TF crop, responsible for
higher grain yield (42%).
Parameters SRI TF LSD0.50
Panicles / m2
439.5 355.2 61.6
Ave. Panicle length, cm 22.5 18.7 2.3
Spikelet / panicle 151.6 107.9 12.9
Filled spikelet, % 89.6 79.3 5.1
1000-grain weight, g 24.7 24.0 0.2
Grain yield, t/ha 6.41 4.50 0.23
HI 0.47 0.32 0.04
DWM(ICAR),IndiaDWM(ICAR),India

20. 0
50
100
150
200
250
300
350
Short Medium Long Extralong
Paniclenumber/m2
Categoryof panicles
SRI TP
Short: >10 cm - 17 cm
Medium: 17.1 cm - 20 cm
Long: 20.1 cm - 24 cm
Extra-long: 24.1 cm - <26 cm
Distribution of panicles according to its length
under SRI and TF
DWM(ICAR),IndiaDWM(ICAR),India

21. Salient findings
Significant changes were observed in the
morphological and physiological characteristics
of SRI plants
• Greater root growth & activity
• Improved shoot growth
• Greater LAI
• Favourable canopy structure
• Higher levels of leaf chlorophyll
• Increasing fluorescence efficiency
• photosynthetic rate
• Delayed senescence
DWM(ICAR),IndiaDWM(ICAR),India

22. These factors contributed to
 larger panicles (more spikelets per panicle),
 better grain setting (higher % of filled
grains)
 heavier individual grains (higher 1000-
grain weight),
 higher grain yield
DWM(ICAR),IndiaDWM(ICAR),India

23. Conclusion
Improvement in grain yield under SRI is
attributable to improved morphology and
physiological features of the rice plant below
and above ground (Better Root-shoot
interaction).
SRI methods narrow the gap between genetic
potential and in-field yield achievements
through management practices.

24. Thanks
Contact: amod_wtcer@yahoo.com