Author: Dr. T. M. Thiyagarajan, Dean Faculty of Agricultural Sciences, SRM Institute of Science and Technology, Kattankulathur, Tamil Nadu, India Title: Understanding the System of Rice Intensification (SRI) for Sustainable Rice Production Presented at: The International Conference on Climate Change, Biodiversity and Sustainable Agriculture Venue: Assam Agricultural University, Jorhat, Assam, India Date: December 13-16

1. Understanding the
System of Rice Intensification (SRI)
for Sustainable Rice Production
Dr. T. M. Thiyagarajan
Dean, Faculty of Agricultural Sciences
SRM Institute of Science and Technology,
Kattankulathur 603203, Tamil Nadu
Former Director, Centre for Soil And Crop Management Studies
Former Dean, Agricultural College & Research Institute, Killkulam
Tamil Nadu Agricultural University

2. Rice is a very well ‘evolved’ crop
• it can be raised by
- throwing or planting dry seeds or sprouted seeds;
- transplanting or throwing of young or older
seedlings;
- planting randomly or in lines at any spacing;
- flooded or alternate wet and dry moisture regimes
- apply different sources and amounts of nutrients.
• So, it grows under very wide range of environments

3. Yield Potential
• The yield of a crop cultivar when grown in environments to
which it is adapted, with nutrients and water not limiting
growth, and with pests and diseases effectively controlled.
• Growing conditions are usually less perfect than that is
required for achieving full genetic potential.
• Genetic potential is the amount of production that a plant is
genetically capable of producing, if all the conditions
required for growth and performance are optimal.

4. THE BEST and IDEAL growing environment for rice to
express its genetic potential
• We probably may never know this, as includes the growing aerial
environment (radiation, temperature, rain, humidity, pests) and the
soil environment (water, nutrients, temperature, chemistry, biology,
drainage, microbiology, inputs) which can vary in innumerable
permutations and combinations, more than are humanly possible
to create and investigate in the field.
• Determining a better environment provided by good management
practices will help us to reach towards genetic potential

5. Approaches to maximize yield potential
• breeding High yielding varieties
• speeding up the multiplication of crop genomes using a
technique called genome doubling.
• transference of C4 plant mechanisms into C3 plants

6. –In the conventional sense : formal, top-down
recommendations for improved varieties, increased
plant densities, and increased use of external inputs
(mineral fertilisers, pesticides), or
–In an agro-ecological sense: a grass-roots movement,
knowledge-intensive, soil-health oriented, building soil
biodiversity, savings on labour and external inputs (seeds
and chemicals); capitalising on farmer know-how to cope
with the location-specificity of farming
Sustainable Rice Production

7. System of Rice Intensification
An agro-ecological and knowledge-based
methodology for increasing the productivity of
irrigated rice by changing the management of
plants, soil, water and nutrients while reducing
dependency on external inputs
* Farmers have developed effective SRI adaptations
for rainfed rice production

8. What is SRI ?
Growing rice with:
Early establishment of seedlings;
Fewer, widely-spaced transplanted population
(although direct-seeded SRI is possible);
Regular intercultivation;
Root-friendly irrigation; and
Supplementation with organic manures

9. System of Rice Intensification
• Provides a different and better growing environment, to
which any cultivar responds positively (although some
respond better than others; local varieties perform well).
• More productive phenotypes are produced which are
characterized by higher number of tillers per plant,
increased plant height, longer and wider leaves, longer
panicles, more grains per panicle, and improved grain
quality.

10. Basic Principles of SRI
• Early and careful crop establishment
• Lower transplant density & population
• Root care: unflooded irrigation
• Soil health care: intercultivation
• Soil biodiversity care : organic manures

11. System of Rice Intensification
• attempts to substantially increase rice yields merely by changing
the way the rice crop is established and managed in the field.
• is based on certain theoretical arguments about the growth
patterns and physiology of rice plants.
• aims to exploit the vigorous growth exhibited by rice plants when
sown thinly in the seedling nursery and transplanted when still very
young, at a low density, into the main field.
• involves the principle that sparse irrigation and soil disturbance –
intended to foster aerobic soil conditions – will stimulate highly
productive interactions between rice roots and beneficial soil micro-
organisms

12. How different are the SRI practices from
conventional practices?

13. Younger Seedlings
Conventional SRI
Age 3 – 5 weeks 8 – 15 days
Nursery area (sq.m to plant 1 ha) 810 100
Seed rate ( kg to plant 1 ha) 20 - 60 7.5
Growth stage Tillering 2-3 leaves
Population density Crowded Sparse
Transplanting shock exists Nil
Tillering potential reduced high
• Young seedlings concept was known earlier with ‘dapog’ method of nursery

14. Single Seedlings per hill and wider spacing
Conventional SRI
No.of seedlings per hill 2 -6 1
Pattern of planting Random / line square
Spacing (cm)
20 x 10, 15 x 10
random
25 x 25
No. of plants at transplanting (per sq.m) 100 – 200+ 16
Tools used Ropes rarely Ropes, markers
• Single seedlings are used in hybrid rice seed production
• ‘Gaja’ method of planting (single seedling and wider spacing) was developed by a Tamil Nadu farmer in
1907
• Single seedling planting was being popularized during 1910s and 1920s in Madras presidency

15. Intercultivation
• Is not generally a recommended practice in rice cultivation
• But a Tamil Nadu farmer practiced intercultivation in 1907
• Intercultivation experiments were conducted in Japan during
1949-52.
• Intercultivation was favoured by a few scientists
• Soil strirring is an important principle in SRI
• In SRI, intercultivation is recommended to be followed until the
canopy closes, at 10-day intervals, whether there are weeds or not
-- the principle is to intercultivate the soil for active soil aeration,
not just to remove weeds; weeds become ‘green manure.’

16. Intercultivation

18. Theories on the effect of Intercultivation
• A kind of physico-chemical change occurs in the soil which
causes decomposition of organic matter in the soil and thus
increases the supply of nutrients
• decreases the amount of toxic gases in the soil and
increases the amount of useful oxygen accessible there at
the same time
• Cutting of roots promotes the growth rate of plants
• The cumulative effect of all these processes is that the final
yield is increased to a great extent.
Nojima (1960)

19. SRI irrigation regime
• Considers not just the plant water requirement, but
also the air requirement of the roots and soil biota.
• Provide the growing plants with sufficient but never
excess water, so that the roots do not suffocate and
degenerate.
• Soil should be mostly aerobic most of time, and not
continuously saturated so as to benefit the growth and
functioning of both plant roots and aerobic soil biota.

20. SRI Crop
Cycle

21. How SRI Creates a Different and
Favourable Growing Environment?

22. The changes brought about in the growing
environment of the plants due to the use of
young single seedlings, wider spacing, soil-
aerating weeder operations, and reduced,
controlled irrigation have been found to have a
positive influence on the growth of plants as well
as on the soil dynamics in a manner not found in
non-SRI cultivation

23. Effects of SRI practices on the above-ground environment
• Soil is exposed to sunlight and atmospheric air frequently
• Availability of more sunlight for the leaves and enhanced
photosynthesis in the canopy
• Photosynthesis is also enabled in lower leaves
• Intercultivation results in some earthing-up effect
• Leaves remain green even after reaching maturity
• Leaves had higher light utilization capacity and greater
photosynthetic rate, especially during the reproductive and
ripening stages of the crop.
• Less incidence of pests and diseases
• Reduction or absence of rodent damage in SRI fields

24. Effects of SRI practices on the
below-ground environment
• Rice plants under SRI can have 10 times more root mass, about 5
times more root length density, and about 7 times more root
volume in the top 30 cm of soil profile, compared with the roots in
plots of flooded rice
• The is less or negligible root degeneration from suffocation
• Mixing aerobic and anaerobic soil horizons by intercultivation
triggers growth
• Significant differences in soil microbial populations; higher levels
of enzyme activity in SRI plant rhizospheres are indicative of
increased N and P availability; also more soil microbial C and N

25. Effect of SRI on crop growth

26. Phenotypical alterations in SRI crop
• More open plant architecture with more erect and larger leaves
• Profuse tillering and more panicles
• Longer panicles, more grains per panicle, higher percentage of
grain-filling
• Higher leaf chlorophyll content at ripening stage
• Delayed senescence or leaves
• Greater fluorescence efficiency
• Higher photosynthesis rate
• Lower rates of transpiration (higher water efficiency)
• More efficient in the uptake and utilization of nitrogen

27. ‘More SRI crop per drop’
• Reductions in irrigation water requirements
by 30-50% per hectare
• Higher water productivity – more output of
grain per unit of water input – by 30-100%

29. Improved
productivity
29%
Less water
requirement
32%
Reduced cost of
cultivation
10-12%
Lower GHG
emission
-1.3 t CO2 eq ha-1
More income
$ 340 ha-1
Benefits of SRI
Details Conv SRI %
Yield (Kg / Ha) 5,400 7,150 32%
Grain revenue
@ $ 15.50 /100 Kg
840 1,112 32%
Straw revenue
@ $ 0.50 /100 Kg
50 65 30%
Total revenue ( $ /
Ha)
890 1177 32%
Total expendi-ture ( $ /
Ha)
476 424 -11%
Net profit ($ / Ha) 414 754 82%
Cost-benefit ratio 1.87 2.78 49%
Conventional SRI
$ 476 $ 424
11% reduction
in expenditure/ha
Effects of SRI

30. Expansion of carbon sinks
• SRI rice plants sequester more carbon, with higher grain and straw
yield, and with more root biomass
• Increased soil organic matter through SRI practices that improve the
soil with more organic matter application and with increased root
exudation into the rhizosphere; this nurtures larger soil biota
• Associated agro-ecological practices sequester carbon, such as green
manure production, integration with agroforestry, surface mulch
applications, etc.
• Reduced carbon footprint due to less use of agrochemicals
(including effects of less manufacturing and shipping of fertilizer)

31. SRI and climate change mitigation
Flooded rice paddies are a major source of
methane (CH4), a greenhouse gas (GHG) that
is roughly 30 times more potent than carbon
dioxide (CO2), the main GHG contributing to
global warming and to climate change.
Rice paddies contribute about 15-20% of the
total methane emissions that human activities
currently generate and propel into the
atmosphere
Creating aerobic soil conditions in rice paddies
can increase the potential for production and
emission of nitrous oxide (N2O). This is a GHG
about 300 times more potent than CO2
Intermittent paddy irrigation by SRI or
AWD reduces methane emissions by
between 22% and 64%
Nitrous oxide increases are not very great
and do not offset or cancel out the
benefits from SRI and AWD reductions in
methane emissions.
Net GHG reductions with intermittent
irrigation have ranged between 20% and
40%, and even up to 73%
A comprehensive analysis of GHG
emissions associated with SRI methods in
India, including CO2, calculated these to
be reduced by 40%
Concerns Findings

32. GHG IMPACT ASSESSMENT: IAMWARM (per year)
 Estimated annual climate change mitigation
benefit due to IAMWARM: 449,984 tons Co2
eq
 Alternate wetting & drying with SRI reduced
GHG emissions by 391,000 tons Co2 eq
Components Without Project With Project Balance
Rice/SRI 14,299.90 6,483.88 - 7,816.03
Livestock 5,906.79 5,841.37 - 65.42
Annual Crops 349.21 -1193.92 - 1,543.14
Units: 000’s tons Co2 eq

33. Resistance to drought, floods, storms, pests, diseases
• Improved drought resistance of SRI plants which thrive
with 30-50% less irrigation water per land area, due to
deeper, larger, less-senescing root systems
• Reduced competition among plants creates stronger
plants above and below ground
• Organic matter-enriched soils are able to store more
water and to furnish nutrients better

34. Practices / Variations / Alternatives
in Adopting SRI Principles

35. Early Crop Establishment
Ideal Practice
Where the principle
may not work or be
adopted?
What is
the alternative?
 Seedlings should not
have more than 2-3
leaves
 8-14 day-old seedlings
under usual conditions
 Saline soils
 Saline irrigation water
 Difficulties in acquiring
/ using young seedlings
 Cold ambient
temperatures
 Use older seedlings,
preferably under 3
weeks old
 Plant 2 or 3 seedlings
per hill
 Follow all other SRI
principles of wider
spacing, intercultivation
and limited irrigation

36. Lower Transplant Density & Population
Ideal Practice
Where the principle may
not work or be adopted?
What is the alternative?
 Single seedling per hill
 Wider spacing: 20 x 20 cm is
the minimal requirement to
enable weeder use; 25x25
cm is more commonly
appropriate; or 30x30 cm if
soil is very fertile
 Square planting to enable
weeder to be used in both
directions (perpendicularly)
 In low organic matter
soils or where high rate
of organic manures
cannot be applied,
greater width should
not be adopted
 Where there is less skill
or non-cooperation of
planting labourers
 20 x 20 cm is sufficient in poor, low
fertility soils
 If the first SRI crop does not allow
3rd intercultivation due to crowded
tillers, spacing should be increased
in the next season
 If square planting is not possible, at
least have wider spacing of rows
 If single seedlings are not possible,
plant not more than 2 per hill
 Follow all other SRI principles

37. Root-friendly Irrigation
Ideal Practice
Where the principle may
not work or be adopted?
What is the alternative?
 Unflooded irrigation to a thin layer,
allowing the water to drain/dry up,
getting the soil exposed to sunlight
until it develops thin cracks. This
practice is followed until flowering.
 After flowering, irrigating with a thin
layer of water and not allowing the
soil to develop cracks. The plants
should not experience water scarcity
 A thin water layer should be
available at time of inter-cultivation
 Impossible to get the
soil exposed to enough
sunlight
 Field always remains
flooded due to
seepage which
saturates soil
 Cascade irrigation
under tank ayacuts
 Ignore SRI irrigation
principle if no
possibility of good
water control.
 Plant 3-week-old
seedlings
 If establishment is in
doubt, plant 2 seedlings
per hill
 Follow other SRI
principles

38. Improving soil quality - Intercultivation
Ideal Practice
Where the principle
may not work or be
adopted?
What is the alternative?
 Using a weeder at 10-day intervals after
transplanting, up to 4 times or until the
canopy closes, whichever is earlier
 Use the weeder in both directions to get
maximum soil aeration
 Weeds that remain after weeder use
should be removed by hand
 Intercultivation should be done even if
there are no weeds, because this controls
weeds pre-emptively, and also aerates the
soil to promote growth of roots and soil
microbes
 Skilled labour is not
available
 Labour is unwilling to
do this work
 Weeder is not
available
 Available weeder is
not suitable for the
kind of soil
 Pay more wages so labourers get
compensated with more income
while farmer has increased profit
 Do weeding at least twice, on
15th and 30th day after
transplanting
 Do weeding in one direction and
after 10 days in the other
direction
 Where there is no square
planting, do weeding 4 times in
one direction and hand-remove
weeds within the rows
 Follow other SRI principles

39. Improving soil quality – Organic manures
Ideal Practice
Where the principle
may not work or be
adopted?
What is the alternative?
 Apply green leaf
manures, cattle
manure, compost,
crop residues to the
extent possible
 Apply biofertilizers
where available
 Non-
availability of
sources of
organic matter
 Grow Gliricidia on the bunds to
have a permanent source of
green leaf manure
 Use available quantities of
organic manure and supplement
with chemical fertilizers
 Fertilizers can be used, but the
tradeoff is less nurturing of the
life in the soil

42. SRI in West Africa

43. SRI in Latin America

44. SRI in Philippines

45. SRI in Lower Mekong Delta

46. Global spread of SRI (2017)

48. Sustainable Sugarcane Initiative (SSI)
EID Parry Company has developed a unique 3-tier nursery programme using
the tissue culture technology. This is integrated with Sustainable Sugarcane
Initiative (SSI) production.
Producing sugarcane seedlings has turned profitable for a farmer, near
Avalpoondurai, in Erode
The SSI method of sugarcane cultivation was evolved from the principles of ‘More with Less’
followed in SRI (System of Rice Intensification) and introduced in India by the WWF-ICRISAT
collaborative project in 2009.
SSI methods can increase sugarcane yields by at least 20% with 30% less water and a 25% reduction
in chemical inputs.

49. System of Millet Intensification - Odisha
System of Millet
Intensification has
increased production of
small and marginal
farmers in PRAGATIi,
Koraput action areas of
Nandapur block

50. System of Wheat Intensification (SWI)
Practiced in Bihar,
Madhya Pradesh,
Rajasthan,
Chhattisgarh, and
Uttarakhand, Nepal,
Pakistan, Ethiopia, and
Mali Superior performance of the direct-seeded
version of SWI on plant height, root length and
volume, grain, straw, and total biological yield,
economic returns, and residual soil fertility.
SWI methods also performed well under adverse
weather conditions in 2012–2013, being able to
sustain wheat production under climatic stress,
demonstrating risk-mitigation and climate-
resilience potential

51. Conclusions
• SRI is a ready opportunity for climate-smart rice production
• Requires no major investments in infrastructure, research or
input subsidies
• Farm families can consume more rice and improve their
incomes within one or two cropping seasons
• Farmers in over 60 countries have seen these effects of SRI
management are applying these new principles.

52. SRI Knowledge Centre (http://sri.cals.cornell.edu)