- SRI is based on four main principles that interact in synergistic ways:
- Establish healthy plants early and carefully, nurturing their root potential.
- Reduce plant populations, giving each plant more room to grow above and below ground and room to capture sunlight and obtain nutrients.
- Enrich the soil with organic matter, keeping it well-aerated to support better growth of roots and more aerobic soil biota.
- Apply water purposefully in ways that favor plant-root and soil-microbial growth, avoiding flooded (anaerobic) soil conditions.
The world record yield for paddy rice production is not held by an agricultural research station or by a large-scale farmer from the United States, but by Sumant Kumar who has a farm of just two hectares in Darveshpura village in the state of Bihar in northern India. His record yield of 22.4 tons per hectare, from a one-acre plot, was achieved with what is known as the System of Rice Intensification (SRI). To put his achievement in perspective, the average paddy yield worldwide is about four tons per hectare. Even with the use of fertilizer, average yields are usually not more than eight tons.
Sumant Kumar’s success was not a fluke. Four of his neighbors, using SRI methods, and all for the first time, matched or exceeded the previous world record from China, 19 tons per hectare. Moreover, they used only modest amounts of inorganic fertilizer and did not need chemical crop protection.
Using SRI methods, smallholding farmers in many countries are starting to get higher yields and greater productivity from their land, labor, seeds, water, and capital, with their crops showing more resilience to the hazards of climate change.1,2 These productivity gains have been achieved simply by changing the ways that farmers manage their plants, soil, water, and nutrients. The effect is to get crop plants to grow larger, healthier, longer-lived root systems, accompanied by increases in the abundance, diversity, and activity of soil organisms. With more than one in seven people on Earth going hungry and demand for rice predicted to outpace supply within two decades, SRI offers real hope of feeding the world without wrecking the environment.
Producing more output with fewer external inputs may sound improbable, but it derives from a shift in emphasis from improving plant genetic potential—whether through engineering or plant breeding—to providing optimal environments for crop growth. SRI methodology translates into a number of irrigated rice cultivation practices that, for most smallholder farmers, include the following:
- Plant young seedlings carefully and singly, giving them wider spacing, usually in a square pattern, so that both roots and canopy have ample room to spread.
- Keep the soil moist but not inundated. Provide sufficient water for plant roots and beneficial soil organisms to grow, but not so much as to suffocate or suppress either (e.g., through alternate wetting and drying or through small but regular applications).
- Add as much compost, mulch, or other organic matter to the soil as possible, feeding the soil so that the soil can, in turn, feed the plant.
- Control weeds with mechanical methods that can incorporate weeds while breaking up the soil’s surface. This actively aerates the root zone as a beneficial by-product of weed control. This practice can promote root growth and the abundance of beneficial soil organisms, adding to yield.
The ideas and method behind SRI were first developed in Madagascar in the 1960s by a French Jesuit priest called Henri de Laulanié. But it was an American professor, Norman Uphoff, director of the International Institute for Food, Agriculture, and Development at Cornell University, who was largely responsible for spreading the word about Laulanié’s work. Given $15 million by an anonymous billionaire to research sustainable development, Uphoff went to Madagascar in 1983 and saw the success of SRI for himself: farmers whose previous yields averaged two tonnes per hectare were harvesting eight tonnes. In 1997 he started to actively promote SRI in Asia, where more than 600 million people are malnourished.
“It is a set of ideas, the absolute opposite to the first green revolution [of the 1960s] which said that you had to change the genes and the soil nutrients to improve yields. That came at a tremendous ecological cost,” says Uphoff.
The first green revolution shielded countries like India from famine by using new crop varieties and large doses of fertilizer and pesticide. “We have tried to make agriculture an industrial enterprise and have forgotten its biological roots,” says Uphoff. SRI offers a more sustainable approach at a far lower cost.
Since then, SRI has shown remarkable capacity to raise smallholders’ rice productivity under a wide variety of conditions around the world: from tropical rainforest regions of Indonesia, to mountainous regions in northeastern Afghanistan, to fertile river basins in India and Pakistan, to the arid conditions of Timbuktu on the edge of the Sahara Desert in Mali. There are now an estimated four to five million farmers using SRI worldwide, with governments in China, India, Indonesia, Cambodia, Sri Lanka, and Vietnam promoting it.
SRI techniques are being adapted to improve the productivity of a wide variety of environmental settings, including the arid conditions that many impoverished farmers are forced to use. It turns out that crops can be productive with less irrigation water or rainfall because taking up SRI recommendations enhances the capacity of soil systems to absorb and provide water (“green water”). SRI practices initially developed to benefit small-scale rice growers are being adapted now for larger-scale production, with methods such as direct seeding instead of transplanting, and with the mechanization of some labor-intensive operations such as weeding.3
SRI can also be applied to other crops with similarly dramatic results (which has led some in India to transform the meaning of the acronym SRI to System of Root Intensification). To take wheat, the next most important crop after rice, the system has been under development since 2008. In India, the People’s Science Institute has been working with wheat farmers in Himachal Pradesh and Uttarakhand states. Yield estimates showed a 91 percent increase for unirrigated plots over usual methods in rain-fed areas, and an 82 percent increase for irrigated areas. The method’s popularity was apparent in Bihar: the pilot project expanded from 415 farmers, mostly women, to 15,808 the following year. Similar experiments in Mali the following year showed less striking results. Still, obtaining a 10 percent higher yield with a 94 percent reduction in seed (10 kilograms/hectare [kg/ha] versus 170 kg/ha), a 40 percent reduction in labor, and a 30 percent reduction in water requirements encouraged farmers to continue with their experiments.
Similar results have been demonstrated with crops ranging from mustard seed, sugarcane, finger millet, maize, to a host of legumes.
There are some criticisms of the approach. Scientists have been unable to reproduce the most recently reported results, which has led to skepticism among some, despite the range of anecdotal proof. Critics also point to how the SRI approach is relatively labor intensive, and resistant to large-scale mechanization. However, there appears to be no shortage of cheap labor in the developing world for the foreseeable future.
In one of his last papers, Laulanié wrote that he developed this method by learning from the rice plant. The rice plant is mon maître (“my teacher”), he wrote. Each of the component activities of SRI has the goal of maximally providing whatever a plant is likely to need in terms of space, light, air, water, and nutrients. It also creates favorable conditions for the growth and prospering of beneficial soil organisms in, on, and around the plant.
The popularity of SRI methods can be attributed to many factors: They are low risk. They don’t require farmers to have access to any unfamiliar technologies. And they save money on multiple inputs, while earning higher yields. Most important is that farmers can readily see the benefits for themselves.
Consequently, many farmers are gaining confidence in their ability to get more from less by modifying their crop-management practices. They can provide for their families’ food security, obtain surpluses, and avoid indebtedness. In the process, they are enhancing the quality of their soil resources and are buffering their crops against the temperature and precipitation stresses of climate change.
- Thakur, AK, Uphoff, N & Antony, E. An assessment of physiological effects of system of rice intensification (SRI) practices compared with recommended rice cultivation practices in India. Experimental Agriculture 46, 77–98 (2009).
- Zhao, LM et al. Influence of the system of rice intensification on rice yield and nitrogen and water use efficiency with different N application rates. Experimental Agriculture 45, 275–286 (2009).
- Sharif, A. Technical adaptations for mechanized SRI production to achieve water saving and increased profitability in Punjab, Pakistan. Paddy and Water Environment 9, 111–119 (2011).