A Review of theSystem of Rice

Intensification (SRI)

Norman Uphoff Cornell International Institute for

Food, Agriculture and Development

for presentation in Mymensingh,September 25, 2002

SRI IS A “WORK IN PROGRESS”

Something new, but only in part; much still to be demonstrated scientifically

While SRI appears ‘too good to be true’ there is much evidence it is ‘for real’

SRI is being used successfully by – a growing number of farmers in – a growing number of countries (15+)

SRI IS A METHODOLOGY rather than a “TECHNOLOGY”

Different paradigm for rice growingManagement produces a different phenotype

SRI is a set of PRINCIPLES that are applied through a set of

PRACTICES that farmers areexpected to adapt to suit their

local conditions

The basic idea of SRI is that RICE PLANTS GROW BEST

(A) When plant ROOTS can grow very large and deep because they have been

• transplanted carefully, i.e., without trauma, with optimally• wide spacing between plants(B) And when rice is grown SOIL that is:• well aerated with abundant and diverse• soil microbial populations

“Starting Points” for SRI• Transplant young seedlings, 8-15 days, quickly and very carefully

• Single plants per hill with wide spacing in a square pattern, 25x25 cm or wider

• No continuous flooding of field during the vegetative growth phase (AWD ok)

• Use rotating hoe early and often (2-4x)

• Recommend application of compost

Practices produce a different PHENOTYPE

OBSERVABLE RESULTS• Average yields about 8 t/ha -- twice the

present world average of 3.8 t/ha• Maximum yields can be twice this; about

16 t/ha, with some over 20 t/ha• Water requirements reducible by 50%• Increased factor productivity for land,

labor, capital and water -- MORE IMPORTANT THAN YIELD

• Lower costs of production per/kgMOST IMPORTANT FOR FARMERS

LESS OR NO NEED FOR:• Different varieties, though best yields from

high-yielding varieties and hybrids; traditional varieties can yield very well

• Chemical fertilizers -- while these give positive yield response with SRI, we find that compost gives best results

• Agrochemicals – plants more resistant to pests and diseases with SRI methods so pesticides, etc. not often needed

FURTHER BENEFITS

• Seeding rate reduced as much as 90%, 5-10 kg/ha yields more than 50-100 kg;

smaller nursery area, less water needed• No lodging because of stronger roots• Environmentally friendly production

due to water saving, no/fewer chemicals• More accessible to poor households

because few capital requirements

DISADVANTAGES / COSTS• SRI is more labor-intensive, at least

initially -- but can become labor-saving?• SRI requires greater knowledge/skill

from farmers to become better decision-makers and managers -- but this is good for human resource development!

• SRI requires good water control to get best results, making regular applications of smaller amounts of water -- but this can be obtained through investments? Maybe not possible in monsoon climate

SRI is COUNTERINTUITIVE• LESS BECOMES MORE -- by utilizing

the potentials and dynamics of biology• Smaller, younger seedlings will give

larger, more productive mature plants• Fewer plants per hill and per m2 can give

more yield • Half the water can give higher yield• Fewer or no external inputs are

associated with greater outputNew phenotypes from existing genotypes

These are remarkable claims• But they reflect experience on farms,

more than on experiment stations• They have some, if not yet complete,

support in the scientific literature• Note: I am not the originator of SRI, just

a proponent for its being evaluated and used where appropriate, now working with many colleagues around the world

• SRI is the due entirely to the work of Fr. Henri de Laulanié, S.J.(1920-1995)

BACKGROUND

• CIIFAD involvement with Tefy Saina began in 1994 around Ranomafana National Park in Madagascar, where yields averaged 2 t/ha

• Previous work by NC State University got average yield up to 3 t/ha, maximum of 5 t/ha

• During 1994-99, Tefy Saina helped farmers average 8 t/ha, with best yields up to 16 t/ha

• Over same period, farmers in French project improving small-scale irrigation on the high plateau had the same results

Spread beyond Madagascar

• Nanjing Agricultural University - 1999

• Agency for Agricultural Research and Development, Indonesia - 1999-2000

• Philippines, Cambodia, Bangladesh etc.

• China Hybrid Rice Center - 2000-2001

• International conference, Sanya, China, April 2001 -- 15 countries represented

Participants at the SRI Conference in Sanya, China

Reports from Sanya ConferenceCOUNTRY No. of Data

Sets/Trials(No. of farmers)

Ave. SRIYield (t/ha)

ComparisonYield (t/ha)

Max. SRIYields (t/ha)

Bangladesh 4 On-farm (261)6 On-station

6.35.25-7.5

4.94.4-5.0

7.15.6-9.5

Cambodia 3 On-farm (427) 4.83.4-6.0

2.72.0-4.0

12.910.0-14.0

China 7 On-station w/hybrid varieties

12.49.7-15.8

10.910-11.8

13.510.5-17.5

Cuba 2 On-farm 9.158.8-9.5

6.25.8-6.6

NR

Gambia 1 On-farm (10)1 On-station

7.16.8-7.4

2.32.0-2.5

8.88.3-9.4

Indonesia 2 On-Farm5 On-station

7.46.2-8.4

5.04.1-6.7

9.07.0-10.3

Madagascar 11 On-farm(3,025)

3 On-station

7.24.2-10.35

2.61.5-3.6

13.95.6-21.0

Philippines 4 On-farm(47)

1 On-station

6.04.95-7.6

3.02.0-3.6

7.47.3-7.6

Sierra Leone 1 On-farm(160)

5.34.9-7.4

2.51.9-3.2

7.4

Sri Lanka 6 On-farm(275)

2 On-station

7.87.6-13.0

3.62.7-4.2

14.311.4-17.0

SIX PROPOSED EXPLANATIONS

(1) Rice is not an aquatic plant, or even hydrophilic

• Although rice can survive under continuous flooding,

• It does not thrive under these [suboptimal] conditions.

Common understanding of riceCommon understanding of rice “Rice “Rice thrivesthrives on land that is water- on land that is water-

saturated or even submerged duringsaturated or even submerged duringpart or part or allall of its growth cycle.” (p. 43) of its growth cycle.” (p. 43)

“Most varieties maintain “Most varieties maintain better growthbetter growthand and produce higher grain yieldsproduce higher grain yields when whengrown in grown in flooded soilflooded soil than when grown than when grownin in unfloodedunflooded soil.” (pp. 297-298). soil.” (pp. 297-298).

S. K. S. K. DeDattaDeDatta, , The Principles and PracticesThe Principles and Practicesof Rice Productionof Rice Production, J . W. Wiley, NY, 1981., J . W. Wiley, NY, 1981.

In In hypoxic soil,hypoxic soil, rice roots remain close to the rice roots remain close to the surface, forming a “mat” with surface, forming a “mat” with about ¾ in the about ¾ in the top 6 cm top 6 cm at 29 DAT (Kirk and at 29 DAT (Kirk and SolivasSolivas 1997) 1997)

Rice plant roots grown in Rice plant roots grown in flooded soilflooded soil form form airairpocketspockets ( (aerenchymaaerenchyma) through the ) through the disintegrationdisintegrationof the cortex (30-40%): “…of the cortex (30-40%): “…disintegration of thedisintegration of thecortex must surely impair the ability of the oldercortex must surely impair the ability of the olderparts of the root to take up nutrients and conveyparts of the root to take up nutrients and conveythem to the stelethem to the stele”” (Kirk and (Kirk and BouldinBouldin 1991) 1991)

In In flooded soil,flooded soil, bothboth irrigated and upland riceirrigated and upland ricevarieties form varieties form aerenchymaaerenchyma, but in , but in unflooded unflooded soil,soil,neitherneither form form aerenchymaaerenchyma ( (PuardPuard et al. 1989) et al. 1989)

Root cross-sections ofRoot cross-sections ofupland (left) and irrigated (right) varietiesupland (left) and irrigated (right) varieties

ORSTOM researchORSTOM research ((PuardPuard et al. 1989) et al. 1989)

AbstractAbstractNature and growth pattern of rice root systemNature and growth pattern of rice root systemunder submerged and unsaturated conditionsunder submerged and unsaturated conditionsS. S. KarKar, S. B. , S. B. VaradeVarade, T. K. , T. K. SubramanyamSubramanyam, and B. P. , and B. P. GhildyalGhildyal,,

I l I l RisoRiso (Italy), 1974, 23:2, 173-179 (Italy), 1974, 23:2, 173-179

Plants of the rice cultivar Plants of the rice cultivar TaichungTaichung (Native) were grown in pots of (Native) were grown in pots ofsandy loam under 2 water regimes in an attempt to identify criticalsandy loam under 2 water regimes in an attempt to identify criticalroot-growth phases. Observations on root number, length, volume,root-growth phases. Observations on root number, length, volume,and dry weight were made at the early and dry weight were made at the early tilleringtillering, active , active tilleringtillering,,maximum maximum tilleringtillering, and reproductive stages., and reproductive stages.

Rice root degeneration,Rice root degeneration, normally unique to submerged conditionsnormally unique to submerged conditions,,increased with advance in plant growth. At stage of flowering,increased with advance in plant growth. At stage of flowering,78%78% had degeneratedhad degenerated. . During the first phase under flooding, andDuring the first phase under flooding, and

throughout the growth period throughout the growth period under unsaturated conditions,under unsaturated conditions,roots rarely degeneratedroots rarely degenerated. (emphasis added). (emphasis added)

Evidence on Root System Development/Degeneration

Evaluated by ‘pull’ test of root resistance (O’Toole and Soemartono 1981)

• Three plants [3-week seedlings, 3/hill, close planting, continuous flooding] averaged 28 kg/hill (Joelibarison 1998)

• Single SRI plants [12-day seedlings, 1/hill, 25x25 cm, aerated soil] averaged 53 kg/hill -- resistance/plant > 5 times

Dry Matter Distribution of Roots in SRI and Conventionally-Grown Plants

at Heading Stage (CNRRI research: Tao et al. 2002)

Root dry weight (g)

Root Activity in SRI and Conventionally-Grown Rice

(Nanjing Agr. Univ. research: Wang et al. 2002)(Wuxianggeng 9 variety)

0

100

200

300

400

500

N-n n-2 Heading Maturity

Development stage

Ox

yg

en

ati

on

ab

ilit

y o

f α -

NA

(ug

/h.g

DW

)

W

S

(2) Tillering in rice is regulated by structural pattern of growth• Understood in terms of PHYLLOCHRONS

-- related to leaf age or degree-days, but more precise and illuminating than ref. to “early, active, or maximum tillering...”

• Discovered by Katayama (1920s-30s), further developed by de Laulanié (1993)

• Under good growing conditions and if the root system is intact, the number of tillers per plant can exceed 100

TilleringTillering process is regulated process is regulatedaccording to according to PHYLLOCHRONSPHYLLOCHRONS

A periodic A periodic interval of plant growthinterval of plant growth common to common toall all gramineaegramineae species -- in rice, from ~5-8 days species -- in rice, from ~5-8 days

A period in which plant produces A period in which plant produces one or moreone or morephytomersphytomers -- unit of tiller, leaf -- unit of tiller, leaf and rootand root -- from -- fromits apical its apical meristem meristem -- up to 20 or 30 in a period-- up to 20 or 30 in a period

PhyllochronsPhyllochrons represent represent biologicalbiological rather than rather thancalendar time calendar time –– they are either lengthened or they are either lengthened orshortened by factors that either shortened by factors that either slow downslow down or orspeed up speed up the plant’s the plant’s “biological clock”“biological clock”

What speeds up the biological clock?

(adapted from Nemoto et al. 1995)

Shorter phyllochrons Longer phyllochrons• Higher temperatures > cold temperatures• Wider spacing > crowding of roots/canopy• More illumination > shading of plants• Nutrient supply in soil > nutrient deficits• Soil penetrability > compaction of soil• Sufficient moisture > drought conditions• Sufficient oxygen > hypoxic soil conditions

(3) Profuse tillering should not be considered unproductive

An negative relationship has been reported in the literature between

• the number of tillers/plant and• the number of grains/panicle This, however, reflects conventional hypoxic growing environments of rice plants, with root degeneration

Comparison of highComparison of high--yield rice in tropical and yield rice in tropical and subtropical environments: I: Determinants of subtropical environments: I: Determinants of

grain and dry matter yieldsgrain and dry matter yieldsJ . Ying, S. J . Ying, S. PengPeng, Q. He, H. Yang, C. Yang, , Q. He, H. Yang, C. Yang,

R. M. R. M. VisperasVisperas, K. G. , K. G. Cassman Cassman Field Crops ResearchField Crops Research, 57 (1998), p. 72., 57 (1998), p. 72.

“…a “…a strongstrong compensation mechanism exists compensation mechanism exists between the two yield components between the two yield components [panicle number and panicle size]” with a [panicle number and panicle size]” with a ““strongstrong negative relationship between the negative relationship between the two components…” (emphasis added)two components…” (emphasis added)

With a large and intact root system and profuse tillering this relationship is positive.

Increased grain fillingresults from a

positive-sum dynamicbetween the growth and vigor

of roots X tillers and leaves

This is what makes it possible to go from 2 t/ha to 8 t/ha

• A synergistic relationship between root development and tillering with each supporting the other’s growth

• Then both together can support increased grain filling

• With good root development, 80% or more effective tillering, more filled grains and higher grain weight

(4) Positive benefits are seen from soil aeration during the

vegetative growth period

(5) SRI capitalizes on the fact that the uptake of N is a

demand-led process

The The rate of uptake of N rate of uptake of N by rice roots by rice roots is is independent independent of theof the N concentrationN concentrationat the roots’ surface (Kirk and at the roots’ surface (Kirk and BouldinBouldin1991).1991).

[Whenever plants have sufficient N,] [Whenever plants have sufficient N,] rice roots ‘downrice roots ‘down--regulate’ their regulate’ their transport system for NHtransport system for NH4+4+ influx influx and/or ‘upand/or ‘up--regulate’ the efflux, regulate’ the efflux, thereby thereby exuding ammonium in excess exuding ammonium in excess of plant needs of plant needs ((Ladha Ladha et al. 1998).et al. 1998).

Paths for Increased Grain Yield in Relation to N Uptake, using QUEFTS

Analytical Model (Barison, 2002)

N Internal Efficiency

0

2000

4000

6000

8000

10000

12000

0 100 200 300

N uptake (kg/ha)

Gra

in y

ield

(kg/

ha)

SRI grain yield(kg/ha)

Conv. grain yield(kg/ha)

Rapid tillering and root growth

• Creates demand for nutrients -- accelerating plant growth after first 5-6 weeks

• Where does supply come from?

• Probably attributable to biological processes and sources; cannot be explained by “chemical” analyses

(6) The contributions of soil microbial activity are likely the foundation

for SRI success“The microbial flora causes a large

number of biochemical changes in the soil that largely determine the fertility of the soil.” (DeDatta, 1981, p. 60, emphasis added)

Biological Nitrogen Fixation?

• BNF can occur with all gramineae species, including rice (Döbereiner 1987, and others)

• In flooded paddies, BNF is limited to anaerobic processes; SRI provides aerobic conditions as well; BNF must be occurring

• Mixing aerobic and anaerobic soil conditions increases BNF (Magdoff and Bouldin 1970)

• Nitrogenase production is suppressed by the use of chemical fertilizers (van Berkum and Sloger 1983)

P SOLUBILIZATION?• P solubilization is increased under

alternating aerobic and anaerobic soil conditions; Turner and Haygarth (2001) measured large increases in soluble organic P with alternate wetting/drying

• “Microbiological weathering” is probably more important than are the geochemical forms of weathering

• Biological weathering processes are probably also increasing the availability of other nutrients such as S, Zn, etc.

MYCORRHIZAL Contributions?

• Fungi cannot grow in anaerobic soil so flooded rice has forfeited the benefits of mycorrhizae for centuries

• Mycorrhizal fungi can increase volume of soil accessed by root up to 100x

• Plants with mycorrhizal associations can grow well with just a fraction of the P supply that “uninfected” plants need

Benefits from Rhizobia in rice now being explored

• Studied where rice and clover grown in rotation in Egypt, for many centuries

• These endophytic bacteria induce more efficient acquisition of N, P, K, Mg, Ca, Zn, etc. in rice (Yanni et al. 2001)

• Rhizobia increase yield and total protein quantity/ha, by producing auxins and other plant-growth promoting hormones -- however, no BNF demonstrated

ROOT EXUDATION

• Farmers report that SRI practices “improve their soil quality” over time -- yields go up rather than down just by adding compost -- hard to explain

• The soils around Ranomafana were evaluated in chemical terms as some of the poorest in the world (Johnson 1994) e.g., 3-4 ppm P, low CEC all horizons

Larger canopies and root systems increase exudation

and rhizodeposition• 30-60% of C fixed in canopy is sent to the

roots, and 20-40% of this exuded or deposited in rhizosphere (Neumann and Römheld 2001, in Pinton et al. 2001)

• Also 20% of plant N is transferred (Brimecombe et al. 2001)

• Roots and shoots are “two-way streets”• However, little is known about exudation in

rice (Wassmann and Aulakh 2000)

SRI Raises More Questions than It Gives ANSWERS

This is a PRACTICE-LED innovation

• Scientists have a challenge/opportunity to develop explanations for observed

phenotypical changes:– Greater root growth

– Greater tillering

– Less senescence of roots and canopy

– Positive correlation: tillering x grain filling

Plant Physical Structure and Light Intensity Distribution

at Heading Stage (CNRRI Research: Tao et al. 2002)

Suggested Focuses for Explanation of SRI Effects

• Root developmentdifferent transplanting, wider spacing & soil aeration; roots ignored

• Soil microbial abundance and activityplant, soil, water & nutrient management, mixing aerobic / anaerobic conditions

MANY OPPORTUNITIES

• SRI is a still “work in progress” invite interest & collaboration -- no IPR

• SRI puts a presumed “biological ceiling” for rice in a different perspective

• Fr. De Laulanié speculated that rice yields could even reach 30 t/ha when we fully utilize phyllochron dynamics

• Exciting time to be a rice scientist!

THANK YOUMore information is available

on the SRI WEB PAGE:

http://ciifad.cornell.edu/sri/

including Sanya conference proceedings

E-MAIL ADDRESSES:

ciifad@cornell.edu

tefysaina@simicro.mg

ntu1@cornell.edu