Rice is grown in warm, waterlogged soil. Farmers traditionally flood rice paddies throughout the growing season - a practice known as continuous flooding - providing ideal conditions for microbes that produce large amounts of methane.
Simple changes to farming practices can significantly decrease these methane emissions, while also reducing the amount of water consumed during the growing season.
Alternate wetting and drying (AWD), the practice of allowing the water table to drop below the soil surface at one or multiple points during a growing season, is an effective alternative to continuous flooding, proven to reduce methane emissions by as much as 48%. The practice is also cost-saving for farmers, as it requires a third less water than continuous flooding and does not compromise yield.
AWD entails the periodic draining of a field to a certain threshold, usually 15 cm below the soil surface, before re-flooding. A perforated tube placed in the soil enables the farmer to monitor the water level below the soil surface to determine when to irrigate. During dry phases, the methane-producing bacteria are inhibited.
Efficient nitrogen use and application of organic inputs to dry soil can further reduce methane emissions.