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The System of Rice Intensification (SRI) -- What It Is, and How/Why
We Think It Works
Norman UphoffCornell International Institute for
Food, Agriculture and Development
More tillers and more than 400 grains per panicle
SRI appears ‘too good to be true’ (like the economist’s $100 bill?)
• It goes against many concepts and beliefs of agronomists and economists: yield ceiling, soil depletion, tradeoffs, 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 (16+)
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
• Water required reducible by about 50%
• Increased factor productivity from land, labor, capital and water ( > yield)
• Lower costs of production -- this is most important for farmers
SRI Data from Sri Lanka SRI Standard
• Yields (tons/ha) 8 4 +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%
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
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 -- these will give a positive yield response with SRI, but 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 gives more than 50-100 kg
• No lodging because of stronger roots, and 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 may become labor-saving• SRI requires greater knowledge/skill
from farmers to become better decision-makers and managers -- but this contri-butes to human resource development
• SRI requires good water control to get best results, making regular applications of smaller amounts of water -- this can be obtained through investments
The basic idea of SRI is thatRICE PLANTS DO BEST when
• Their ROOTS grow large and deep since they were transplanted carefully and the seedlings experienced little trauma, and with wider spacing between plants; and
• They can grow in SOIL that is 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 -- 2 to 4 times
• 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 -- 150-250+ grains• Higher GRAIN WEIGHT -- often 5-10%• A POSITIVE CORRELATION between
tillers/plant and grains/panicle
SRI goes against LOGIC• LESS PRODUCES 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 as much water gives higher yield• Fewer or no external inputs are
associated with greater outputNew 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, Bangladesh, Cuba, 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
• 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?
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%
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)
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
Critical Factor is Root Growth• 3/4 of rice roots in continuously flooded soil
remain in top 6 cm (Kirk and Solivas 1997)• 3/4 of rice roots in continuously flooded soil
degenerate by time of flowering (Kar 1974)• 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 degenerate
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)
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)
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 vigorous root growth,
• TILLERING can be much greater
• This can be explained in terms of phyllochrons -- interval of plant growth found in all “grass” species
• Discovered by Japanese scientist Katayama in 1920s-30s
• Tillering pattern follows sequence of ‘Fibonacci series’ --1, 1, 2, 3, 5, 8, 13...
What speeds up the biological clock?
(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
What is essential to speed up the biological clock?
• Use of YOUNG SEEDLINGS -- best to transplant during ‘window of opportunity’ before 4th phyllochron
• Rice plants can respond best to other favorable conditions if minimally disturbed during transplantation
• This suggests that DIRECT SEEDING may work as well as transplanting and lower labor needs -- should evaluate
With best growing conditions, the phyllochrons are shorter
• So more periods of growth can be completed before the rice plant switches from
• its vegetative growth phase• to its reproductive phase• 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
• This assumes that rice plants will take up more N if it is easier for them to access N because of higher concentrations of N in the root zone
• Demand-Driven Model for Promoting Growth
• Manage plants so as to accelerate their rate of growth
• This reflects an under-standing that increased plant demand for N is what 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
0
2000
4000
6000
8000
10000
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 are observed from 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 nitrogen (N) from air into forms available to plant roots
• Research has shown that when aerobic soil and anaerobic soil are mixed, rather than having only aerobic soil or only anaerobic soil, BNF increases greatly (Magdoff and Bouldin, 1970)
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 for the higher yields observed; not enough N measured in the soil
• The use of chemical fertilizers inhibits the production by roots and microbes of nitrogenase, the enzyme needed for BNF (van Berkum and Sloger 1983)
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 contra-saison crop -- not on rice crop?
• Both crops reportedly gave better yield• This makes no sense if LEACHING and
VOLATILIZATION are big problems, or if nutrients are ‘used up’ by plants
• It makes sense, however, for BNF
OPTIMUM RATES OF N FERTILIZER APPLICATION
Duration Early Medium Late100-110 days 111-120 days 121-135 days
Varieties 60 60 60Optimum NApplication 150-200 150 100Yield (t/ha) 5.36 5.64 5.76
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 lowlandgermplasm. Field Crops Research, 56, 41-71.
Phosphorus Solubilization• Aerobic bacteria can acquire phosphorus
from unflooded soil for their own use• When the soil is flooded, these bacteria die
(lyse) and release their contents into the water that permeates the soil
• When the soil dries again, surviving bacteria begin their growth again
• Soluble P can increase by 185-1,900% by such ‘mining’ of the soil that increases nutrient supply (Turner & Haygarth, 2001)
Microbiological ‘Weathering’ of Soil?
• Soluble P can increase by 185-1,900% by microbiological ‘mining’ of the soil (Turner & Haygarth, 2001)
• Speculation that this process operates increase supply of other nutrients too
• Under ‘natural’ conditions, ‘depletion’ of soil is very rare occurrence -- due to microbiological processes
Mycorrhizal Associations• Mycorrhizal funguses ‘infect’ plant roots
• They send out hyphae (filaments/threads) in all directions and expand the volume of soil that the plant can extract nutrients from by 10-100 times
• Mycorrhizae are very good at harvesting phosphorus -- increased efficiency by 60x
• Mycorrhizae cannot grow in anaerobic soil conditions, so cannot benefit irrigated rice
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• 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
SRI Supports the Motto of Organic Farmers
• Don’t try to feed the plant --
• Feed the soil -- and the soil will feed the plant
• Emphasis on symbiosis between plants and soil microorganisms
SRI can be seen as an agronomic system for:
• 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 will be found in the 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)
Microbes grow better in: • SOIL not continuously flooded,• with more soil organic matter
Microbes benefit from exudation resulting from more 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
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