History and main ideas of SRI
Assembly of the practices that culminated in SRI began in the 1960s based on Fr. de Laulanie's observation of 'positive-deviant' farmer practices, starting with planting single seedlings instead of multiple seedlings in a clump, and not keeping irrigated paddy fields flooded during the rice plants' vegetative growth stage. Planting with wider spacing in a square pattern, rather than randomly or in rows, followed, as did controlling weed growth by use of a soil-aerating push-weeder (rotating hoe).
In 1983, the beneficial effect of transplanting very young seedlings, less than 15 days old, was discovered serendipitously. Subsequently, when fertilizer prices increased, compost made from any decomposed biomass turned out to give even better results than chemical fertilizer. SRI concepts and practices continue to evolve as they are being adapted to rain-fed (unirrigated) conditions and with transplanting being superseded by direct-seeding sometimes.
The synthesis of SRI has proceeded empirically, but the central principles for getting best results are:
- rice field soils should be kept moist rather than continuously saturated, minimizing anaerobic conditions, as this improves root growth and supports the growth and diversity of aerobic soil organisms;
- rice plants should be spaced optimally widely to permit more growth of roots and canopy and to keep all leaves photosynthetically active; and
- rice seedlings should be transplanted when young, less than 15 days old with just two leaves, quickly, shallow and carefully, to avoid trauma to roots and to minimize transplant shock.
These changes from conventional practice when managing plants, soil, water and nutrients induce more productive phenotypes from any rice genotype, although some varieties respond better than others to SRI methods. Increased yield is achieved with 80-90% reductions in seed requirements (lower plant population) and 25-50% less irrigation water. Chemical fertilizer and agrochemical crop protection can be used, but best results can be attained without use of purchased inputs.[cita
Weed growth will be higher in these fields due to the absence of standing water. But since the rice plants are planted with wider spaces between rows, a rotary weeder can be drawn in between the rows of plants to remove the weeds and also aerate the soil. On the 10 day after planting weeds may not be prominent, but its better to weed so that the weeds do not get a chance to assimilate the nutrients. Modified weeders such as the conoweeder are available. In Kerala, India the technique has been adopted by some people owing to the pressure from the Department of Agriculture and Mithraniketan ( an NGO Krishi Vignan Kendra located at Trivandrum). Failure are attributed to poor water management, non use of rotary weeder and use of older seedlings.
Spread of SRI
The spread of SRI from Madagascar to around the globe has been credited to Norman Uphoff, director of the International Institute for Food, Agriculture and Development at Cornell University, Ithaca, New York from 1990 to 2005. In 1993, Uphoff met officials from Association Tefy Saina, the non-governmental organisation set up in Madagascar in 1990 by de Laulanie to promote SRI. After seeing the success of SRI for three years when Malagasy farmers previously averaging 2 tons/hectare averaged 8 tons/hectare with SRI, Uphoff became persuaded of the merits of the system, and in 1997 started to promote SRI in Asia. As of 2007, the beneficial effects of SRI methods had been documented in 28 countries, most recently in Bhutan, Iraq, Iran and Zambia. Governments in the largest rice-producing countries (China, India and Indonesia) are now supporting SRI extension. In India, SRI concepts and practices have been extrapolated successfully to other crops such as sugar cane, finger millet and wheat.
 Cases of Success
Several cases of success are reported in Kerala, India. The program has proven successful in Nellanad Gramapanchayat in Thiruvananthapuram. Agricultural Officers including Sreekala, Sreekumari, and Geethakumari have several cases of success.
There are criticisms of SRI. While supporters of SRI report many benefits in addition to yield increase—resistance to pests and diseases, resistance to abiotic stresses like drought and storm damage, more output of polished rice (in kg) when SRI paddy (unmilled rice) is processed (bushels), less chemical pollution of soil and water resources—critics have focused on yield suggesting that claims of increase are due to "poor record keeping and unscientific thinking". Some critics have suggested that SRI success is unique to soil conditions in Madagascar, a point that is disputed by supporters.
Critics have objected that there is a lack of details on the methodology used in trials and a lack of publications in the peer-reviewed literature. This latter deficiency is now being remedied by such publications, but systematic trials that will satisfy scientific critics remain to be done. A global field trial is planned for 2009–2011, to be conducted by researchers from Cornell University, Wageningen University, and the International Rice Research Institute 
Additionally, the reliance on weeding/tilling machinery may limit the system's applicability.
The SYSTEM of
known as SRI – also as le Systéme de Riziculture Intensive in French and la Sistema Intensivo de Cultivo Arrocero* (SICA) in Spanish -- is a methodology for increasing the productivity of irrigated rice cultivation by changing the management of plants, soil, water and nutrients. SRI practices lead to healthier, more productive soil and plants by supporting greater root growth and by nurturing the abundance and diversity of soil organisms. The agroecological principles that contribute to SRI effectiveness have good scientific bases. SRI concepts and methods have been successfully adapted to upland unirrigated rice, and they are now being extrapolated to other crops like millet, wheat and sugar cane.
SRI does not require the purchase of new seeds or the use of new high-yielding varieties. Although the highest yields with SRI have been obtained from improved varieties, most traditional or local varieties of rice respond well to SRI practices and command a higher market price. And while chemical fertilizer and agrochemicals can be applied with SRI, their use is not required as organic materials (compost, manure or any decomposed vegetation) can give good or even better results at low cost. Farmers report that when SRI methods are used correctly, rice plants are better able to resist damage from pests and diseases, reducing or eliminating need for agrochemical protection.
Because plant populations are greatly reduced with SRI, seed costs are cut by 80-90%, and because paddy fields are not kept continuously flooded, there are water savings of 25 to 50%, a major benefit in many places. However, cessation of flooding means that increased weeding is required. If this is done with soil-aerating implements like a rotating hoe, this cost has a benefit of enhanced crop production.
SRI does require skillful management of the factors of production and, at least initially, more labor, particularly for careful transplanting and for weeding. Since yield increases are usually 50 to 100%, and possibly several times present levels, the returns to labor can be very great. The profitability of rice production can be greatly increased when yield goes up with a reduction in the costs of production. As farmers gain skill and confidence in SRI methods, their labor input in fact decreases, and over time SRI can even become labor saving compared with conventional rice-growing methods.
SRI is a work in progress, with improvements continually being made, including better implements and techniques that further reduce labor requirements. Farmers are encouraged to make their own improvements in SRI methods and to share experience within the farming community. Yield is the most evident (and controversial) feature of SRI, but many other considerations are also driving its spread around the world. Additional information on SRI benefits such as resistance to drought and storm damage, shorter time to maturity, and more milled rice resulting when SRI paddy is processed can be found in a paper on: Features of the System of Rice Intensification apart from Increases in Yield.
SRI increases rice production and raises the productivity of land, labor, water and capital through different practices for managing:
Rice plants - Seedlings are transplanted:
- very young -- usually just 8-12 days old, with just two small leaves
- carefully and quickly to have minimum trauma to the roots
- singly, only one per hill instead of 3-4 together to avoid root competition
- widely spaced to encourage greater root and canopy growth
- in a square grid pattern, 25x25 cm or wider -- 30x30 cm or 40x40 cm, even up to 50x50 cm with the best quality soil
Soil - This is kept moist but well-drained and aerated, with good structure and enough organic matter to support increased biological activity. The quality and health of the soil is the key to best production.
Water - Only a minimum of water is applied during the vegetative growth period, and then only a thin layer of water is maintained on the field during the flowering and grain filling stage. Alternatively, to save labor time, some farmers flood and drain (dry) their fields in 3-5 day cycles with good results. Best water management practices depend on soil type, labor availability and other factors, so farmers should experiment on how best to apply the principle of having moist but well-drained soil while thier rice plants are growing.
Nutrients - Soil nutrient supplies should be augmented, preferably with compost, made from any available biomass. Better quality compost such as with manure can give additional yield advantages. Chemical fertilizer can be used and gives better results than with no nutrient amendments, but it contributes less to good soil structure and active microbial communities in the rhizosphere than does organic matter. At least initially, nutrient amendments may not be necessary to achieve higher yields with the other SRI practices, but it is desirable to build up soil fertility over time. Rice-root exudation, greater with SRI, enhances soil fertility.
Weeds - Since weeds become a problem in fields that are not kept flooded, weeding is necessary at least once or twice, starting 10-12 days after transplanting, and preferably 3 or 4 times before the canopy closes. Using a rotary hoe -- a simple, inexpensive, mechanical push-weeder has the advantage of aerating the soil at the same time that weeds are eliminated. (They are left in the soil to decompose so their nutrients are not lost.) Additional weedings beyond two increase yield more than enough under most conditions to justify the added labor costs. A variety of available weeders are shown in the WASSAN publication "Weeders: A Reference Compendium."For more details, see one of the "manuals" on SRI that are available in Cambodian, English, French, Nepali, Spanish, Thaiand other languages. ("Manuals" is put in quotation marks because we do not think of or promote SRI as a technology with a fixed set of practices; it is not a "package" to be adopted in a fixed way.) There are a number of variations in the practices that should be considered and evaluated under field conditions.
SRI has the disadvantage of sounding "too good to be true." This is the main reason why it was not taken seriously by agricultural scientists for many years, though this is now changing. Also, it is hard for farmers to believe, for example, that they can get twice as much yield by using only 5 to 10 kg of seed per hectare instead of the 50 to 100 kg per hectare they are used to using -- or that they can achieve this by using only about half as much irrigation water. Additional benefits of SRI are outlined in the 2005 Uphoff article: Features of the System of Rice Intensification apart from Increases in Yield (10p, pdf).
SRI methods increase the productivity of:
- water -- since yields can double or more with only half as much water, the productivity of water is greatly increased -- this is especially important in countries or places where water is becoming scarcer;
- land -- yields as indicated above can average about 8 t/ha once the methods are used correctly, and can be twice that or more when they are used with precision and skill;
- labor -- SRI does require more labor - about 26% in one Madagascar evaluation, 11% in a Sri Lankan survey - but depending on the cost of labor, the value of increased production increases the returns to labor by at least 50% and often several hundred percent. Once the methods have been mastered, the labor requirements for SRI decline. Also, implements are being developed that save labor. In Cambodia, over half the farmers using SRI now report that is is labor-saving for them.
Environmental Benefits: SRI is environmentally-friendly. Reduced demand for water frees up water for other uses; soil that is not kept saturated has greater biodiversity. Unflooded paddies do not produce methane, one of the major "greenhouse gases" that are contributing to global warming. There can be more nitrous oxide from unflooded paddies, which offsets to some extent the gains from reducing methane emissions, but when nitrogen fertilizer is not used, this effect should be small. On balance, SRI should improve environmental conditions.
Equity Considerations: SRI also has the benefit of being particularly accessible for farmers who have small landholdings and need to get the highest yields possible from their available land. Since poorer households have relatively more labor compared to land, SRI is one of the few agricultural innovations that has a bias in favor of equity. It is true that very poor households may find it difficult to invest labor in SRI because they need to be earning daily incomes, even if their returns to labor would be higher from SRI. However, since returns to land, labor and water are all higher with SRI, any household that grows rice and is labor-constrained will do better by using SRI methods on just a part of its landholding, using its other land for production of other crops when labor is available.
Active Role for Farmers: SRI methods are most productive when used with skill and care, so there will probably continue to be long-term advantage for labor-intensive production with SRI. However, SRI should be seen as a set of principles that are applied through various techniques, rather than as a fixed technology to be adopted as a "package." There is synergy among practices that makes their use together more beneficial than just using certain of the practices; but any of the practices should give some improvement in yield. We anticipate that various kinds of mechanization will over time make SRI suitable for larger scaler production.
Farmers are encouraged to experiment with the methods and to evaluate the results for themselves, not just to "adopt" SRI. The best spacing between plants, for example, needs to be determined in relation to particular soil, climatic, hydrological and other conditions. Exactly when and how to apply water depends on soil characteristics and field position. So recommendations for spacing, water management, age of seedling, etc. are not offered as universal. Instead, principles are presented -- to be understood, tested and adapted by users to suit their own conditions. It is hoped that what farmers learn from using SRI may help them to become more innovative producers in other respects.
Grain Quality: When SRi paddy is milled, the outturn if often proving to be higher, as there are fewer unfilled grains (less chaff) and fewer broken grains (becasue they resist shattering). In Andhra Pradesh, India, the rice millers association is promoting SRI and paying a higher rice per bushel, as outturn has gone from about 67% to about 75%. The sugar cooperative in Cuba that has pioneered the new production methods in that country reports that its outturn has gone up from 60% before to 68-71% now with SRI. This adds about 15% more productivity on top of the higher yields of paddy.
Faster Maturing: Farmers are finding that SRI methods often, though not always, reduce the time required for grain maturation. In Camboida, on average, SRI crops are ripening about 7 days sooner than regular crops of the same variety. In Andhra Pradesh, India, ripening is 7-10 days sooner. (It has been alleged that SRI crops take longer to mature, but this is not the experience in the field.) In Nepal during monsoon season 2004, farmers got more than a doubling of yield (3.37 to 7.85 t/ha) with a 15-day reduction in time to maturity. Being able to harvest sooner reduces farmers' risks of damage from pests or from typhoons, cyclones or other extreme weather than can come the end of the season.
Health Benefits: By reducing the application of agrochemicals in rice production, the resulting grain has little or no chemical residues. No systematic nutritional analyses have been done yet on SRI grains, but the larger root systems could enhance their micronutrient content, suggested by the higher grain wieght and greater resistance to shattering. Many things are still not known about SRI in technical terms. This page will be updated as more information becomes available.