Rice is the staple food of 3 billion people, providing one-fifth of calories consumed worldwide. Its cultivation is responsible for at least 10 percent of agricultural greenhouse gas emissions and 9 to 19 percent of global methane emissions. That is because flooded rice paddies are ideal anaerobic environments for methane-producing microbes that feed on decomposing organic matter, a process known as methanogenesis.
The System of Rice Intensification (SRI), developed on Madagascar in the 1980s, is a holistic approach for sustainable rice cultivation. It calls for:
- Planting single seedlings with more space between them, rather than by the handful and bunched closely together.
- Watering intermittently and allowing for dry spells, rather than using continuous flooding.
- Tending plots with a rotating hoe, to address weeds and aerate soil, and applying compost.
These methods benefit soil and root systems while lowering the inputs required for production and increasing crop yields. Now practiced by 4 million to 5 million farmers around the world, SRI yields are 50 to 100 percent higher than conventional rice production. Seed use drops by 80 to 90 percent and water inputs by 25 to 50 percent. Farm incomes can double, as methane emissions drop and soils sequester carbon.
Project Drawdown defines System of Rice Intensification (SRI) as: an agroecological rice production technique that uses minimal water during the initial stage (just a thin layer), and alternates wetting and drying during the later stage, to increase yield gain and reduce emissions. This practice replaces conventional paddy rice production on smallholdings.
SRI emerged in Madagascar in the 1980s and has become widespread among smallholders, particularly in Asia. SRI’s unique system leads to significant savings in water consumption and enables a more aerobic environment in the rice growth cycle, resulting in reduced methane emissions. Improvement in both organic and inorganic nutrients under SRI result in improved soil conditions, increasing nutrient availability and holding capacity of the soil. Thus, less external fertilizer is required, which in turn reduces the emissions associated with the inefficient use of nitrogen fertilizers.
System of Rice Intensification offers more than 40 percent yield gain, water conservation, lower labor requirements, cost savings, and a better operational environment. The increased yield from the same piece of land could also reduce land clearing for rice cultivation and associated emissions.
SRI has spread rapidly via grassroots, farmer-to-farmer networks. It is currently limited to smallholder rice areas, and adoption should be a high mitigation priority in those areas.
SRI has been adopted largely by smallholder farmers and has much higher yield benefits compared to improved rice production. We calculate that SRI can expand from 8.4 million acres to 133 million acres by 2050, both sequestering carbon and avoiding methane emissions that together total 3.1 gigatons of carbon dioxide or its equivalent over thirty years. With increased yields, 477 million additional tons of rice could be produced, earning farmers an additional $678 billion in pro t by 2050.