Exploring the Impact of Alternate Wetting and Drying and the System of Rice Intensification on Greenhouse Gas Emissions: A Review of Rice Cultivation Practices

Abstract

Rice provides ~20% of human dietary energy and, for many people, a similar share of their protein. Rice cultivation, however, produces significant greenhouse gas (GHG) emissions, comparable to those from the aviation sector. The main GHG from rice production is methane, mostly a result of conventional rice cultivation (CRC) keeping rice fields continuously flooded during the crop cycle. There is extensive evidence that alternate wetting and drying (AWD) of rice fields substantially reduces methane emissions. AWD is one component of the System of Rice Intensification (SRI), an agroecological approach to the management of plants, water, soil, and nutrients. This article reviews field studies measuring GHG emissions associated with the adoption of AWD and SRI. The review confirms that both AWD and SRI offer substantial reductions in methane emissions per hectare compared with CRC. These benefits are, however, partly offset by increases in emissions of nitrous oxide and carbon dioxide. The studies also show that SRI (but not AWD) improves yield and therefore further reduces GHG emissions per kg of rice. The review concludes that while both AWD and SRI substantially reduce emissions per hectare and per kilogram of rice, SRI can simultaneously contribute to food security while addressing the drivers of climate change. Further investigation of carbon emissions and sequestration under different rice cultivation methods is needed to strengthen the evidence base.

Policy and law: the case of synthetic nitrogen fertilizer

“…Farmers in developing countries obtain consistently high yield ratios when they use intensive agroecological techniques (Badgley et al 2007, 92). These methods can also reduce GHG emissions (Burney et al 2010, 12052, Dahlgreen andParr 2024) and increase carbon sequestration (Das et al 2023).…”

Introduction to Special Issue on “The System of Rice Intensification (SRI)—Contributions to Agricultural Sustainability”

“…• Climate change: This article reviews all of the studies found in the published literature that assess how much the emission of greenhouse gases from rice paddies is reduced by alternate-wetting-and-drying irrigation (AWD) and/or by SRI crop management, which includes AWD [27]. This effect is particularly important for reducing the generation of methane (CH 4 ), the greenhouse gas that contributes most quickly and most potently to global warming.…”