- What is SRI
The System of Rice Intensification, or SRI — le Système de Riziculture Intensive in French and la Sistema Intensivo de Cultivo Arrocero (SICA) in Spanish — is a climate-smart and agroecological methodology to increase the productivity of irrigated rice (and, more recently, other crops) by changing the management of plants, soil, water and nutrients. Using the SRI methodology, yields are increased by 20-50% or more, while reducing inputs: seed by 90%, irrigation water by 30-50%, chemical fertilizer by 20-100%, and usually reduced need for pesticides. For the farmer, SRI brings greater returns to labor, land and capital.
WHAT ARE THE UNDERLYING PRINCIPLES OR SRI?
SRI methodology is based on four main, interacting principles:
- Establishing plants early and quickly, to favor healthy and vigorous root and vegetative plant growth.
- Maintaining low plant density to allow optimal development of each individual plant and to minimize competitions between plants for nutrients, water and sunlight.
- Enriching soils with organic matter to improve nutrient and water holding capacity, increase microbial life in the soil, and to provide a good substrate for roots to grow and develop,
- Reducing and controlling the application of water, providing only as much water as necessary for optimal plant development and to favor aerobic soil conditions.
Based on these principles, farmers adapt SRI practices to their climate zone, and to their agroecological and socioeconomic conditions. Most common adaptations respond to soil conditions, water control, changing weather patterns, access to organic inputs, the decision to practice fully organic agriculture or not, access to labor, mechanization, and other socioeconomic factors.
In addition to irrigated rice, the SRI principles have been applied to rain fed rice and to other crops, such as wheat, sugarcane, teff, finger millet, mustard, and pulses all of which show increased productivity over current conventional planting practices. When SRI principles are applied to other crops, we refer to it as the System of Crop Intensification or SCI (see SCI section of the website for details.)
What are the key SRI practices for irrigated rice?
The key SRI practices for irrigated rice production are summarized below.
|Cultivation Practices||Standard Methods||SRI Methods|
|Seed Selection and preparation||Seeds are not selected or treated||Seeds are soaked for 24 hours prior to seeding to eliminate non-viable seeds|
|Nursery management||Flooded nurseries, densely seeded||Non-flooded nurseries, often raised beds,
|Age of seedlings when planted||21-30 days, sometimes up to 60 days||8-12 days, representing the 2-leaf stage|
|Spacing||Hills are 10-15 cm apart, in rows or
|Hills in square pattern, with spacing 25x25cm or more|
|Number of plants/hill||3-5 plants/hill; 130-500 plants per m2||1 plant/hill (<16 plants per m2)|
|Water management||Continuous flooding of fields
during crop cycle
|Alternate wetting and drying|
|Weed control||Hand weeding, or herbicide use||Mechanical weeding, aerating the soil|
|Fertilization||Reliance on chemical fertilizers||Organic matter as base fertilization, complemented if needed with chemical fertilizer|
Recommended SRI management practices for irrigated conditions
Seed treatment and nursery management:
Seeds are soaked in a large container of water for 24 hours. Viable seeds sink to the bottom and non-viable seeds float to the surface, and can easily be removed. Seeds are sown non-densely in a seedbed with good soil structure. Each plant has space to grow, and roots can develop easily and will not get entangled with each other.
Transplanting young seedlings at the 2 leaf-stage. Seedlings are grown in a non-flooded nursery and removed carefully with minimal trauma to the roots. Seedlings should be replanted quickly and carefully, at a shallow depth of only 1-2 cm deep, assuring that the roots are not dried out or damaged. Some adaptations for direct-seeding and mechanical transplanting have been developed in a number of countries.
Reducing plant density through i) planting one seedling per hill, and ii) increased spacing between the plants, usually at 25cm x 25 cm, planted in a square pattern. In less fertile soils and with low tillering rice varieties, spacing can be reduced to 20cm x 20cm, with profusely tillering rice varieties and organic matter enriched soils, spacing can be increased to 30cm x 30cm, or possibly to 35cm x 35cm (rarely more).
Reducing irrigation water application:
Only a shallow water layer of 1-2 cm is introduced into the paddy field during the vegetative period. The plot is left to dry until cracks become visible, when another thin layer of water is introduced. This is called ‘intermittent irrigation’ or ‘Alternative Wetting and Drying’ (AWD). During flowering, a thin layer of water is maintained, followed by AWD during the grain filling period, before draining the paddy 2-3 weeks before harvest. Some farmers irrigate every evening, others leave the fields to dry over a 3-8-day period, depending on soil and climate conditions, and control over irrigation water. The drying period creates aerobic conditions allowing roots to better develop.
Enhancing soil organic matter
The soils are enriched with organic matter to improve soil structure, nutrient and water holding capacity, and to favor soil microbial development. Adding organic matter represents the base fertilization, which is complemented if needed by fertilizer, most often urea. Most common organic matter sources are compost, animal manure, green manure, and crop residues such as rice straw.
Controlling weeds is done through mechanical weeding, mostly done with a simple push-weeder. Weeds grow more vigorously under non- flooded field conditions, and need to be kept under control from an early stage.
Frequent use of the mechanical weeder is ideal, up to 4 times starting at 10 days after transplanting and repeated every 7-10 days until the canopy is closing. Mechanical weeding has multiple functions and benefits:
- Incorporation of weeds into the soil, where their nutrients are recycled
- Superficial tillage improves soil aeration
- Root growth is stimulated through some root pruning and soil aeration
- As water, organic matter and soils are mixed anew and oxygenized through the weeding process, nutrients become better available to the plants. A re-greening effect of the plants can be observed 1-2 days after weeding.
- A redistribution of water across the plot through the weeding process, contributes to a continuous leveling of the plot and eliminates water patches in lower laying areas in the field that create anaerobic conditions for the plants.
The use of the weeder creates homogeneous field conditions, a more uniform crop stand and leads to increased yields.
Overview Publication: More Rice for People, More Water for the Planet
This publication details experiences from Oxfam America, World Wildlife Fund (WWF), and Africare, including what farmers and policy makers say about SRI, the relevance of SRI to climate change, and reports from Mali, Vietnam and India showing SRI impacts in very different climatic and cultural contexts.
- WHAT ARE THE MAIN ENVIRONMENTAL, ECONOMIC, AND SOCIAL BENEFITS OF APPLYING THE SRI METHODOLOGY?
Benefits include increased yields of 20-50% or more, a reduction in seed use of 80-90%, and up to 50% water savings. SRI methods have shown these significant benefits across all ecological zones in over 50 countries, and have been adopted largely by smallholder farmers in Asia, Africa, and Latin America and the Caribbean.
By reducing inputs of seed, water, chemical fertilizers, and in some cases of labor, SRI gives greater returns to farmers’ available resources of land, water, labor and capital, and can lower their production costs. This increases farmers’ income and increases the profitability of rice farming.
Use of pesticides can be decreased because SRI plants are stronger and healthier. Disease pressure is reduced when plants are widely spaced because humidity levels in the plant canopy are lower than in more densely planted conventional fields.
Use of chemical fertilizer can be reduced significantly as fertilizer use efficiency increases in soils enriched with organic matter. As soils improve in structure and become more fertile through periodic organic matter amendments, less fertilizer is needed to achieve a targeted production level. If the soil is sufficiently fertile, use of chemical fertilizer can be eliminated.
Because plants are stronger and more deeply rooted, SRI crop stands show greater resilience towards drought, strong winds and storms. These hazards are becoming more frequent and more extreme with climate change.
Also, farmers note that SRI management usually shortens their crop cycle by 1-2 weeks. This frees up their land for other uses, and reduces their crops’ exposure to climatic stresses and pest and disease risks.
SRI paddy rice usually produces about 10% higher outturn of polished rice when milled, because of fewer unfilled grains and less chaff. Fuller grains, reduced chalkiness and reduced breakage of grains during milling, further improves grain quality, which translates often in a higher price and return for the farmer.
Additional environmental benefits include:
- Increased water availability at the landscape level or for other consumption needs, as irrigation water use can be reduced by up to 50% with SRI management,
- Improved soil and water quality, through the reduction of agrochemical use,
- Increase in soil carbon pools through the additions of organic matter to soils and residues from larger root systems.
- Reduction in methane emissions from rice paddies through non-flooded rice paddy conditions; thus far, although more research is needed, evaluations have not shown any offsetting increase in nitrous oxide emissions.
- Maintaining the biodiversity of rice cultivars can be enhanced, as local varieties become more productive and thus more attractive for farmers to grow.
- WHERE DID SRI ORIGINATE?
SRI was developed in Madagascar by a French priest, Father Henri de Laulanié, S.J., who spent 34 years (1961-1995) working with farmers there to improve rural livelihoods through increased rice productivity. The main practices of SRI were synthesized by the mid-1980s. With Malagasy colleagues, Laulanié established a local non-profit, Association Tefy Saina, in 1990, which promoted the knowledge of the SRI methodology and its use as part of a holistic rural development strategy.
- HOW HAS THE SRI METHODOLOGY SPREAD AROUND THE WORLD?
Tefy Saina and the Cornell International Institute for Food, Agriculture and Development (CIIFAD) began working together in 1994 on a USAID-funded project to conserve the rainforest ecosystem of Ranomafana. Following three years of on-farm comparisons, which showed consistent increases in farmers’ yields from 2 tons/ha to 8 tons/hectare, CIIFAD first began bringing the SRI methodology to international attention after 1997.
Outside Madagascar, higher rice productivity using SRI methods was first validated in China and Indonesia during 1999-2000. The following year, similar results were reported from Cambodia, Philippines, Cuba, Sri Lanka, India, Myanmar, the Gambia, and Sierra Leone. By 2002, SRI methods had been validated in 15 countries; by early 2013, this number had grown to 51, including most of South and Southeast Asia, and also various countries in sub-Saharan Africa, the Middle East, and Latin America and Caribbean (see SRI countries).
The SRI website maintained at Cornell University by the SRI International Network and Resources Center (SRI-Rice) has catalyzed widespread distribution of SRI information — experiences, problems, solutions, innovations, etc. – supported by extensive and continuous email communication among members of the international network. Jim Carrey’s Better U Foundation supports the work of SRI-Rice to catalyze worldwide spread of SRI methodology and practice. Within many countries, SRI users have formed their own networks, including list-serves, websites, or blogs. All SRI information is freely available and open access.
The knowledge and practice of SRI has spread through the efforts of a growing network of interested persons and institutions: NGOs, universities or research institutions, government agencies, the private sector; and most of all by farmers themselves. CIIFAD has played a central role in networking and knowledge-sharing since 2000.
- HOW DOES SRI BENEFIT POOR HOUSEHOLDS?
Poor households usually have very limited access to land and capital, so raising yield per unit area with reduced outside inputs is of great importance. The first objective for poor farmers is usually to feed their own families. Higher yields of 20-50% or more have a significant impact on farm families’ food security. When food security is assured, households can diversify their economic activities, either on-farm or off-farm.
As SRI is a knowledge-based intensification method, poor farmers are less dependent on outside inputs and can improve their agricultural crop production with locally available resources. Once the SRI methodology is adopted by a large segment of the farmers, it can be expected that with more local rice available and reaching markets in greater abundance, the urban poor will also benefit from lower rice prices and good-quality local rice, and being less exposed to fluctuating prices of imported rice.
It should be noted that SRI has spread most quickly among poorer producers, which in turn has led governments, research organizations and development agencies to pay attention to this novel approach to agricultural intensification as a poverty-reduction strategy, with positive environmental benefits, particularly water-saving.
- HOW CAN SRI ALSO BENEFIT LARGER FARMERS?
Because SRI capitalizes on biological processes, on the genetic potentials of the crop, and on the plant-soil-microbial interactions, its application and benefits are scale-neutral. The SRI principles for intensifying agriculture are available to any producer, who can adapt the cropping practices to suit local conditions. Efforts to mechanize transplanting, direct-seeding, and weeding are underway in a number of countries for small-scale to large-scale agriculture. We expect that SRI principles will soon be utilized at different scales.
- CAN SRI OUTPERFORM “BEST MANAGEMENT PRACTICES”?
It has been argued that SRI may improve upon farmers’ original practices, but not above the best management practices proposed by rice scientists. There are reports by farmers of exceptionally high yields by a SRI farmer in Bihar state in India and elsewhere, but yield is not the only factor that matters in crop production. Best management practices often depend heavily upon outside resources such as improved seeds in large quantities for densely planted fields, and large amounts of water and agrochemicals. SRI practices optimize the use of local resources, and significantly reduce the amount of seeds, water and agrochemicals needed, while at the same time increasing yields.
- DOES SRI REQUIRE SPECIFIC PLANT VARIETIES?
SRI methodology is a management approach, and does not require new varieties. Improved plant performance can be observed with practically any variety when cultivated with SRI methods. This is because the plants can better express their genetic potential when grown in a more optimal environment. High-yielding varieties or traditional ones, hybrids or landraces, all perform better when planted with SRI methods, although some varieties respond better than others.
Farmers show greater interest in growing local varieties when using the SRI methodology, as their higher yield level makes them more profitable. Farmers often prefer local varieties for their adaptation to local soil and climate conditions, and better pest and disease resistance. Most consumers prefer them for their taste. SRI methods allow farmers to maintain and increase the diversity of planted rice varieties, something that has been diminishing in recent years.
- DOES SRI HAVE ANYTHING TO DO WITH GENETICALLY-MODIFIED ORGANISMS (GMOS)?
SRI gains are achieved through better crop management and can be observed with any variety, although invariably some varieties respond and perform better than others under SRI management. Thus, SRI methods could be used with GMOs, as SRI is also used with hybrids. Currently, no GM rice is planted commercially worldwide, but advances on developing and testing GM rice are made, for instance with the beta-carotene enriched Golden Rice.
As SRI yield improvements and other benefits are greater than what is usually expected from making genetic modifications, the SRI system can be considered a direct alternative to GMOs. Especially when considering the time and large funding necessary to develop GMOs, the SRI method offers the advantage that it can be applied immediately with little or no additional costs, with farmers’ varieties and local resources. There are no intellectual property rights involved, and this option is available for anyone. It makes the high investments in the development and use of GMOs less urgent for meeting world food needs.
- IS SRI AN “ORGANIC” SYSTEM OF PRODUCTION?
Enriching and improving soils with organic matter is one of the four basic principles of SRI. As soils are improved through organic matter additions, many nutrients become available to the plant from the organic matter. Additionally, the soils are able to hold more nutrients in the rooting zone and release them when the plants need them. Depending on the yield level and on the farming system, some farmers use exclusive organic fertilization for their SRI plots. The majority of farmers complement the organic matter amendment with chemical fertilizers, most often urea, in order to achieve a balanced fertilization of the crop.
We note that when chemical fertilizers cannot reach rural communities due to political instabilities, destructive climate events, or infrastructure problems, or are unaffordable for poor farmers, SRI farmers have the knowledge to produce high rice yields, whereas with conventional farming methods, dependence on external inputs makes farmers more vulnerable to outside events or the constraints of poverty.
- WHAT ARE THE REASONS FOR FARMERS TO CHANGE THEIR CURRENT RICE-GROWING PRACTICES?
Smallholder farmers in Africa, Asia and Latin America often find it difficult to improve their production following conventional intensification recommendations. The Green Revolution paradigm, in its original or revised forms, requires improved seeds, fertilizers and other chemical inputs, which are often unaffordable or unavailable to farmers.
Many farmers who have used chemical fertilizers experience stagnation and decrease in crop productivity over time, as their soils’ fertility is slowly diminishing. This is a result of substituting improving soil fertility naturally with the exclusive use of fertilizers.
Thus, the SRI methodology is an alternative that represents a new direction of regaining agricultural productivity through ecological and natural processes. Many smallholders in Africa, Asia and Latin America are quickly ready to test the practices and adapt them to their conditions. In most cases, it has been farmers themselves who have taken the lead in spreading and refining these new crop management ideas, followed only later by technicians and researchers.