0210 A Review of the System of Rice Intensification (SRI)

A Review of the System 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 growing

Management produces a different phenotype

SRI is a set of PRINCIPLES

that are applied through a set of

PRACTICES that farmers are

expected 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/kg MOST 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 m 2 can give more yield

Half the water can give higher yield

Fewer or no external inputs are associated with greater output

New 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 Conference

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.

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)

(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

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

With a large and intact root system and profuse tillering

this relationship is positive.

Increased grain filling

results from a

positive-sum dynamic

between 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

Paths for Increased Grain Yield in Relation to N Uptake, using QUEFTS Analytical Model (Barison, 2002)

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)