0302 A New Paradigm for Rice and Why We Think It Works

SRI -- The System of Rice Intensification:

A New Paradigm for Rice and Why We Think It Works

Norman UphoffCornell International Institute for

Food, Agriculture and Development

More tillers and more than 400 grains per panicle

SRI is ‘too good to be true’-- like the economist’s $100 bill

• It contradicts some concepts and beliefs of agronomists and economists: yield ceiling, soil depletion, tradeoffs, genetic determinism, diminishing returns, etc.

• However, there is increasing evidence that SRI greatly raises rice productivity

• SRI is being used successfully by – a growing number of farmers in – a growing number of countries

An Evolving Technology like Aviation

• First flight at Kitty Hawk, NC, broke the gravity constraint -- “heavier than air”

• Improvements on propellor powering of aircraft -- wing design, engines, etc.

• Technology was ahead of science -- same for SRI -- only up to DC-3 stage now

• Can advance to jet propulsion? -- break the sound barrier? -- “faster than sound”

• Soil microbiology may “jet-power” SRI

OBSERVABLE BENEFITS• Average yields about 8 t/ha --

twice present world average of 3.8 t/ha• Maximum yields can be twice this -- 15-

16 t/ha, with some over 20 t/ha• Reduced water requirements ~ 50%• Lower costs of production -- this is

most important for farmers• Increased factor productivity of land,

labor, capital and water -- THIS IS THE MOST IMPORTANT CONSIDERATION

SRI Data from Sri Lanka SRI Standard

• Yields (tons/ha) 8.0 4.2 +88%

• Market price (Rs/ton) 1,500 1,300 +15%

• Total cash cost (Rs/ha) 18,000 22,000 -18%

• Gross returns (Rs/ha) 120,000 58,500 +74%

• Net profit (Rs/ha) 102,000 36,500 +180%

• Family labor earnings Increased with SRI

• Water savings 40-50% of standard method

Data from Dr. Janaiah Aldas, formerly economist at IRRI, now at Indira Gandhi Development Studies Institute, Mumbai, based on visit to Sri Lanka and interviews with SRI farmers, October, 2002

SRI FIELD DAY REPORT, October 28, 2002, AgriculturalTraining Institute, Department of Agriculture, at Universityof Southern Mindanao, Cotabato, Kabacan, Philippines

Production Analysis PSB Rc 72H PSB Rc 82 PSB Rc 18Plants=Hills/m2 16 16 16Panicles/hill 20 25.8 31Grains/panicle 191 155 159Grains/hill 3,825 4,822 4,921Yield/m2 1.16 1.25 1.2Yield (t/ha) 11.6 12.5 12.0

Economic Analysis Pesos/ha Pesos/ha Pesos/haInputs: seeds, org. fertiliz. 3,700 3,320 3,320Other expenses 5,830 5,830 5,830Harvesting, threshing 14,848 16,000 15,360Total Expenses/ha 24,378 25,150 24,510vs. Income @ 8 P/ha 93,800 100,000 96,000Net Income/ha 68,422 74,850 71,490 Rate of Return 280% 298% 292%

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

from high-yielding varieties and hybrids -- traditional varieties produce 4-10+ t/ha

• Chemical fertilizers -- with SRI, these give a positive yield response, but the best results are obtained with compost

• Agrochemicals – plants more resistant to pests and diseases with SRI methods

ADDITIONAL BENEFITS• Seeding rate reduced as much as 90%,

5-10 kg/ha yields more than 50-100 kg

• No lodging because of stronger roots; also stronger panicles (pedicules)

• 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 -- this contributes to human resource development

• SRI requires good water control to get best results, making regular applications of smaller amounts of water -- this can be achieved through investments

RICE PLANTS DO BEST when• Their ROOTS grow large and deep having

been transplanted carefully with the seedlings experiencing little trauma, and with wider spacing between plants; and

• They can grow in SOIL kept well aerated -- never continuously saturated -- with abundant and diverse populations of soil microbes that aid in plant nutrition

‘Starting Points’ for SRI:• Transplant young seedlings, 8-15 days (2

leaves), 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)• Weeding with rotating hoe early (10 DAT)

and often -- up to 4 times, aerate soil

• Application of compost is recommended

These are adapted to local situations

SRI practices produce a different RICE PHENOTYPE:

• Profuse TILLERING -- 30 to 50/plant, 80-100 possible, sometimes 100+

• Greater ROOT GROWTH -- 5-6x more resistance (kg/plant) for uprooting

• Larger PANICLES -- 150-300+ grains• Often higher GRAIN WEIGHT ~ 5-10%• A POSITIVE CORRELATION between

tillers/plant and grains/panicle

Comparison of high-yield rice in tropical andComparison of high-yield rice in tropical andsubtropical environments: I: Determinants ofsubtropical 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. CassmanCassmanField Crops ResearchField Crops Research, 57 (1998), p. 72., 57 (1998), p. 72.

“…a “…a strong compensation mechanismstrong compensation mechanism exists existsbetween the two yield componentsbetween the two yield components[panicle number and panicle size]” with a[panicle number and panicle size]” with a““strong negative relationshipstrong negative relationship between the between thetwo components…” (emphasis added)two components…” (emphasis added)

SRI goes against LOGIC• LESS PRODUCES MORE -- by utilizing

the potentials and dynamics of biology• Smaller, younger seedlings become

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

more yield if other conditions right• Half as much water gives higher yield• Greater output is achieved by using

fewer or no external inputs New plant types from existing genomes

Plant Physical Structure and Light Intensity Distribution

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

These results more often come from farms than experiment stations

• But increasing number of scientists working on SRI -- in China, Indonesia, India, Cuba, Bangladesh, etc.

• SRI is the due entirely to the work of Fr. Henri de Laulanié, S.J.(1920-1995) -- trained in agriculture at INA (1937-1939)

• He lived and worked with farmers in Madagascar (1961-1995), SRI from 1983

• SRI being promoted by Malagasy NGO, Association Tefy Saina, assisted by CIIFAD

Spread beyond Madagascar• Nanjing Agricultural University - 1999;

then CNHRRDC (2000), CNRRI (2001), SAAS (2001), and now others in China

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

• Philippines, Cambodia, Sri Lanka, etc.• International conference, Sanya, China,

April 2001 -- 15 countries reported on experience with SRI

Data 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

Average Yields Impressive:Certain Cases Hard to Explain

• Indonesia -- West Timor (ADRA) • Yield with current methods -- 4.4 t/ha• Yield with SRI methods -- 11.7 t/ha Peru -- Pucallpa, jungle area• Previous yields -- 2 t/ha, with more labor• SRI yield -- 8 t/ha, with less labor + Ratoon crop = 70% of first crop (5.5 t/ha)• Benin -- controlled trial: 1.6 vs. 7.5 t/ha

WHAT IS GOING ON?

Great Variations in Yield

• FRUSTRATING for scientists who think in mechanistic way, regarding rice as a closed system

• But it is EXCITING for scientists who view world in biological way, seeing rice as an open system -- explain variations in terms of the interaction of plants x microbes?

Factorial Trials Evaluating 6 Factors

• Variety: HYV (2798) vs. local (riz rouge) or Soil quality: better (clay) vs. poorer (loam)

• Water mgmt: aerated vs. saturated soil

• Seedling age: 8 days vs. 16 or 20 days

• Plants per hill: 1/hill vs. 3/hill

• Fertilization: compost vs. NPK vs. none

• Spacing: 25x25cm vs. 30x30cm (NS diff.)

6 replications: 2.5x2.5m plots (N=288, 240)

Effect of Young SeedlingsBetter Poorer

SS/20/3/NPK 3.00 2.04

SS/ 8 /3/NPK 7.16 3.89

SS/ 8 /1/NPK 8.13 4.36

AS/ 8 /3/NPK 8.15 4.44

AS/ 8 /3/Comp 6.86 3.61

SS/ 8 /1/Comp 7.70 4.07

AS/ 8 /1/NPK 8.77 5.00

AS/ 8 /1/Comp 10.35 6.39

Results of Factorial Trials(ceteris paribus effects)

Seedling Age 16/20 8 t/ha

Morondava (288) 2.61 3.96 +1.35

Anjomakely (240) 3.80 6.78 +2.48

Water Management Flood Control t/ha

Morondava (288) 2.86 3.71 +0.85

Anjomakely (240) 4.34 5.75 +1.41

More Factorial Results

Plants per Hill 3 1 t/ha

Morondava (288) 3.05 3.51 +0.46

Anjomakely (240) 4.65 5.43 +0.78

Com-Nutrient Amendments NPK post t/ha

Morondava (half HYV) 3.69 3.96 +0.27

Anjomakely (all trad’l.) 4.48 5.49 +1.01

Rice is Rice is not an aquatic plantnot an aquatic plant The standard understanding of rice is that:The standard understanding of rice is that: “Rice “Rice thrivesthrives on land that is water- on land that is water-

saturated or even submerged during partsaturated or even submerged during partor all of its growth cycle.” (p. 43)or all of its growth cycle.” (p. 43)

“Most varieties maintain “Most varieties maintain better growthbetter growth and andproduce higher grain yieldsproduce higher grain yields when grown in when grown inflooded soil than when grown in flooded soil than when grown in unfloodedunfloodedsoil.” (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.

ROOTS HAVE BEEN LARGELY IGNORED BY

PLANT SCIENTISTS

• E.g., in DeDatta’s book on rice, chapter on The Growth, Development and Morphology of the Rice Plant has only 8 lines on roots out of 390 lines of text

• With not a single entry on roots in the 16-page index with over 1100 entries (one brief entry on rhizosphere)

Root Growth is Critical Factor• 3/4 of rice roots in continuously flooded soil

remain in top 6 cm (Kirk and Solivas 1997)• Air pockets (aerenchyma) form in roots of

rice plants when continuously flooded• These air pockets enable rice plants to

survive under submerged conditions• But submerged plants do not thrive --

lacking oxygen, their roots die back• 3/4 of rice roots in continuously flooded soil

degenerate by time of flowering (Kar 1974)

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 degenerationRice root degeneration, normally unique to submerged conditions,, normally unique to submerged conditions,increased with advance in plant growth.increased with advance in plant growth. At stage of flowering, At stage of flowering,78% had degenerated78% had degenerated.. During the first phase under flooding,During the first phase under flooding,and throughout the growth period and throughout the growth period under unsaturated conditions,under unsaturated conditions,roots rarely degeneratedroots rarely degenerated.. (emphasis added) (emphasis added)

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

With young transplants and with vigorous root growth,

TILLERING can be much greater• Can explain in terms of phyllochrons --

interval of growth in all gramineae

• Discovered in 1920s-30s by Japanese scientist Katayama (published 1951)

• Tillering pattern follows sequence of ‘Fibonacci series’ --1, 1, 2, 3, 5, 8, 13… provided that the root system is intact

What is the ‘objective’ of the rice plant?

• Reproduction to produce at least some seed -- plant is not seeking to maximize production

• When plant encounters conditions that threaten its ability to reach maturity and produce seed, growth slows and phyllochrons lengthen

“Biological clock” in rice = rate of cell division/growth

(adapted from Nemoto et al. 1995)

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

ENABLING CONDITIONS

• Soil temperature -- need warmth; flooding reflects solar radiation

• Spacing -- affects shading in canopy, roots’ access to nutrients = crowding slows plant growth

• Oxygen and moisture -- negative correlation -- manage water so as to optimize both growth factors

Key factor is use of YOUNG SEEDLINGS

• Best to transplant during the ‘window of opportunity’ -- before the 4th phyllochron

• Rice plants respond BEST to favorable conditions if their roots were minimally disturbed during transplantation

• This suggests that DIRECT SEEDING can work as well as transplanting and lower labor needs -- should be evaluated

With better growing conditions the phyllochrons are shorter

• The rice plant can complete more periods of growth before it switches from:

• (a) its vegetative growth -- to • (b) reproduction & grain filling• With more tillering, there is

also more root development

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).

Alternative Models for Nitrogen Uptake

• Supply-Side Model to Increase Growth

• Apply N to the soil to raise N availability

• Assumption: rice plants will take up more N if it is easier for them to have access to N because of higher concentrations of N in the root zone

• Demand-Driven Model for Promoting Growth

• Manage the plants in ways that will accelerate their rate of growth

• Assumption: increased plant demand for N induces the roots to take up more N

Paths for Increased Grain Yield inRelation to N Uptake, using QUEFTS

Analytical Model (Barison, 2002)

N Internal Efficiency

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2000

4000

6000

8000

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12000

0 100 200 300

N uptake (kg/ha)

Gra

in y

ield

(k

g/h

a)

SRI grain yield

(kg/ha)

Conv. grain yield(kg/ha)

Benefits can be seen from active soil aeration during the

vegetative growth period

Soil microbial activity is critical for plant nutrition

and SRI performance

“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)

Bacteria, funguses, protozoa, amoeba, actinomycetes, etc.

• Decompose organic matter, making nutrients available

• Acquire nutrients that are unavailable to plant roots

• Improve soil structure and health (water retention, pathogen control)

Biological Nitrogen Fixation

• Microorganisms -- particularly bacteria, both aerobic and anaerobic -- can fix N from the air, converting it into forms that are available to plant roots

• BNF increases greatly when aerobic and anaerobic soil horizons are mixed -- compared to soil that is only aerobic or only anaerobic (Magdoff & Bouldin, 1970) [SRI practices mix aerobic/anaerobic soil]

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, while SRI provides aerobic conditions as well

• BNF must be occurring to get the higher yields observed; not enough N measured in the soil

• Chemical fertilizers inhibit the production by roots and by microbes of the enzyme needed for BNF (nitrogenase)

AZOSPIRILLUM POPULATIONS, TILLERING AND RICE YIELDS ASSOCIATED WITH DIFFERENT CULTIVATION PRACTICES

AND NUTRIENT AMENDMENTSResults of trials at the Centre for Diffusion of Agricultural Intensification,

Beforona, Madagascar, 2000 (Raobelison, 2000)

Azospirillum in theCLAY SOIL (better) Rhizosphere

(103/ml)Roots

(103/mg)Tillers/plant

Yield(t/ha)

Traditional cultivation,no amendments

25 65 17 1.8

SRI cultivation, withno amendments

25 1,100 45 6.1

SRI cultivation, withNPK amendments

25 450 68 9.0

SRI cultivation, withcompost amendments

25 1,400 78 10.5

LOAM SOIL (poorer)SRI cultivation, withno amendments

25 75 32 2.1

SRI cultivation, withcompost amendments

25 2,000 47 6.6

This helps to solve puzzle• Why were many Madagascar farmers

putting their compost for SRI on their preceding vegetable crop -- rather than on their rice crop?

• Both crops reportedly gave better yields• If LEACHING and VOLATILIZATION are

big problems, or if nutrients are ‘used up’ by plants, this makes no sense

• If BNF is occurring, it makes good sense

OPTIMUM RATES OF N FERTILIZERAPPLICATION FOR EARLY, MEDIUM ANDLATE MATURING RICE VARIETIES

Duration Early Medium Late100-110

days111-120

days121-135

daysVarieties 60 60 60Optimum NApplication 150-200 150 100

Yield (t/ha) 5.36 5.64 5.76

Data reported in or calculated from: J. K. Ladha, G. J. D. Kirk, J. Bennett,S. Peng, C. K. Reddy, P. M. Reddy and U. Singh (1998). Opportunities forincreased nitrogen-use efficiency from improved lowland germplasm.Field Crops Research, 56, 41-71.

Phosphorus Solubilization• Bacteria acquire phosphorus and other

nutrients from the soil for their own use• When the soil is flooded, aerobic bacteria

die (lyse) and release their contents into the water that permeates the soil

• When the soil is dried again, the surviving aerobes begin their growth again; repeat

• Soluble P can increase by 185 - 1,900% by such ‘mining’ of the soil that increases nutrient supply (Turner & Haygarth, 2001)

Concept of Microbiological Weathering of Soil

• This process could increase the supply of other nutrients too -- different from and faster than geochemical weathering

• Under natural conditions, ‘depletion’ of the soil is not common

• CIRAD research in Vietnam getting 4 t/ha rice yield on acid soils (pH 3) not improved by applying 100 t/ha lime, using GM/mulch, water mgmt, P, etc.

Mycorrhizal Associations• Mycorrhizal funguses ‘infect’ plant roots,

sending send out hyphae (filaments) in all directions

• They expand the volume of soil that the plant extracts nutrients from by 10-100 x

• Mycorrhizae are very good at harvesting P -- can increase P efficiency by > 50 x?

• Mycorrhizae cannot grow in anaerobic soil conditions, so cannot benefit irrigated rice

Benefits from Rhizobia in rice now being explored

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

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

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

ROOT EXUDATION• Plant stems & roots are two-way streets• 30-60% of the energy (sugars, proteins)

made in the canopy is sent to the roots (Pinton et al., 2000)

• 20-40% of this energy supply is exuded by the roots into the soil, feeding the bacteria, funguses, etc. in the root zone

• Root cells also die and provide energy to microbes through rhizodeposition

• Plants gain more than they lose from this

PROTOZOA• Are said by microbiologists to

“graze” on the bacteria on the roots of plants

• Require lower C/N ratio, so they excrete unneeded N -- on roots

• Increased root exudation would increase bacterial populations -- and also protozoan populations?

SRI Is Supports the Advice of Organic Farmers:

• Instead of feeding the plant --

• Feed the soil -- and the soil will feed the plant

• Support symbiosis between plants and soil microorganisms

• This process has evolved over several 100 million years

SRI can thus be understood as an agronomic system

that integrates:• Plant management -- young seedlings,

careful transplanting, wide spacing• Soil and water management -- leveling,

‘minimum of water’ for soil aeration• Nutrient management -- increase SOM• Microorganism management -- result of

the above, promoted by root exudation

SRI Raises More Questionsthan we have answers for

• Many of the answers we think will be found in growth and functioning of ROOTS which grow better from:

• YOUNG SEEDLINGS, with• WIDE SPACING, and in• AERATED SOIL

Answers will also be found in SOIL MICROBIAL DYNAMICS -- in the abundance & diversity of soil microbes (bacteria, fungi, protozoa, actinomycetes, etc.)

Microbes will grow better in: • SOIL not continuously flooded,• with more soil organic matter

Microbes benefit from exudation due to greater root growth

THANK YOUMore information is available

on the SRI WEB PAGE:

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

including Sanya conference proceedings,

available on CD ROM discs

E-MAIL ADDRESSES:

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