In Europe, rice (467 000 ha) is under permanently flooded (PF) conditions using irrigation waters of major rivers. Climate change, which has led to a greater fluctuation in river flows, is a major challenge to rice production systems, which depend on large and consistent water supplies. In addition, PF rice fields emit greenhouse gases (GHG), such as methane (CH4), that have a strong global warming potential.
Facing climate change and water scarcity in Europe, GreenRice investigates the alternate wetting and drying system (AWDS): irrigation is applied to obtain 2 to 5 cm of field water depth, and then turned off. The intermittent irrigation can save water (by 15-30%) while reducing greenhouse gas emission (up to 48%).
The project aims to design and test an alternative water-saving rice production system for Europe ensuring sufficient productivity while reducing the negative impacts for the environment.
The objectives of GreenRice are to:
- Evaluate the consequences of a shift from a permanently flooded system (PFS) to an alternate AWDS on the rice environment and productivity.
- Identify varieties that maintain their productivity in AWDS.
- Investigate plant traits determining adaption to AWDS.
- Disseminate the results of the projects to the main stakeholders (farmers and natural park authorities) and to the scientific community.
- Field trials involving 12 varieties were conducted in Italy, France and Spain to compare permanently flooded (PF) and alternate wetting and drying (AWD) systems. They showed a large water economy but contrasted varietal responses in term of productivity across countries depending on the irrigation management.
- In 2015, in Italy, AWD systems reduced methane emissions by almost half. There was a significant difference in how the 12 varieties responded to a lower soil water depth. Overall, there was no significant difference observed in soil CO2 fluxes or carbon allocation between the two treatments, except for a few varieties. The data on greenhouse gases (GHG) emission of the 2016 trials are still being analysed.
- Under AWD treatment, rice plants showed an increased root branching, mostly involving the large lateral roots. The arbuscular mycorrhizal phenotype was nicely maintained, even if the colonisation success was slightly more limited than under purely aerobic conditions. Molecular analysis revealed that a phosphate transporter was highly upregulated in AWD plants.