This water-conserving, emission-reducing, and cost-saving practice can help farmers, but challenges still remain for widespread adoption.
A new paper published in Nature Food by an international team of scientists proposes that an innovative rice irrigation methodology, known as Alternate Wetting and Drying (AWD), has significant potential to transform rice farming globally, contributing to enhanced water productivity while maintaining high yields.
The paper, ‘Improved alternate wetting and drying irrigation increases global water productivity’, was conducted by a team of researchers from Peking University, University of Exeter, University of California Davis, Potsdam Institute for Climate Impact Research, Yangzhou University, Columbia University, and the International Rice Research Institute. Analyzing data from over 1,100 field observations, the study found that strategic drying periods between irrigation cycles could save significant amounts of irrigation water without compromising rice production.
The high water cost of rice
Rice is a staple food for nearly half of the world’s population, but it is also the most water-intensive cereal crop, consuming around 30% of global irrigation resources. As water scarcity becomes a global challenge due to climate change, resource degradation, and competition from cities, researchers are seeking sustainable solutions to ensure food security without depleting freshwater supplies.
AWD is a water-saving irrigation technique that allows rice fields to dry intermittently instead of being continuously flooded. By reflooding fields only when soil water potential reaches a certain threshold, AWD can optimize water use while minimizing potential yield loss. The method contrasts with traditional continuous flooding, which keeps rice paddies submerged throughout the growing season.
Environmental and economic benefits
The research analyzed data from 1,187 paired field experiments comparing AWD to traditional flooding techniques. It showed that AWD can increase water productivity across 37% of the world’s irrigated rice fields, particularly in India, Bangladesh, and central China. AWD could also reduce irrigation water use by up to 25% without negatively affecting rice yields in most areas.
Beyond water conservation, AWD has the potential to reduce greenhouse gas emissions. Traditional flooded rice fields are a major source of methane emissions, a potent greenhouse gas. By introducing controlled drying periods, AWD reduces methane production while maintaining productivity. Additionally, the approach could lower irrigation costs for farmers, making rice cultivation more economically viable in water-scarce regions.
However, the study also showed that the success of AWD depends on soil water potential, with optimal thresholds varying by region and soil type. Some soil conditions, such as alkaline soils, may require additional management adjustments to prevent yield losses.
Barriers to adoption
Despite its benefits, AWD adoption has been slow in some regions due to concerns about yield stability and potential yield losses, particularly in certain soil conditions like alkaline soils. AWD also requires careful monitoring of soil water potential, which may be difficult for farmers accustomed to visually checking water levels. Deep-rooted traditional farming practices, lack of awareness of AWD, and limited access to monitoring tools have hindered widespread adoption, compounded by policy and support gaps in various areas and regions.
Future food and water security
These findings highlight the potential of AWD to promote more sustainable rice production systems and provide a pathway toward the sustainable intensification of rice cultivation worldwide. With proper implementation, AWD could help balance the competing demands for water between agriculture and other sectors, helping ensure that future generations will have enough to eat and drink.
