Sustainable and environmental friendly rice cultivation systems in Europe

Summary

In Europe, rice (467 000 ha) is gown 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.

This challenge will become more acute in the future, with increased demands for rice both from within Europe (net deficit of 0.86 Mt) and from overseas. Rice yields under existing production practices are therefore threatened by scarcer water availability. In addition, PF rice fields emit greenhouse gases (GHG), such as methane (CH4), that have a strong global warming potential.

Alternate wetting and drying (AWD) is a system in which irrigation is applied to obtain 2 to 5 cm of field water depth, and then turned off. After a short period (normally 2 to 7 days), when the field has dried out, water is re-applied. Preliminary studies suggest that AWD can reduce water use by up to 30 %, with no net loss in yield provided varieties well adapted to AWD are used, while CH4 emissions can be reduced by up to 48 %.

However, uncertainties still remain as to the impacts of AWDS on GHG fluxes (e.g. CO2, N2O) and plant-mutualist and plant-pest interactions, which may influence the overall efficacy and viability of this new system. Thus, while AWD represents a potentially exciting alternative water management strategy for European rice production, a more complete agronomic, ecological and biogeochemical assessment of AWD is required to evaluate the benefits of the system.

To close these critical knowledge gaps, GreenRice aims to test AWDS in Italy, Spain and France, in regions that are representative of the diversity of European rice growing areas, notably in deltaic areas where rice systems and natural protected wetlands are interdependent.

We will evaluate the agronomic and environmental consequences of shifting from a PF to an AWD system, focusing on rice yields, water consumption, soil salinization, plant-soil-microbial interactions and GHG dynamics. We will identify varieties that maintain their productivity under AWDS through whole genome association mapping of a large panel of temperate varieties, using genomic selection to predict the values of additional breeding lines.

We will investigate traits determining adaptation to AWDS, such as root development, AM colonisation, salt tolerance and resistance to nematodes; and the role of AM symbiosis in alleviating the impacts of biotic stress. An extensive gene expression study will identify the root types and genes important in transport process and the degree to which they are affected by AWDS. The role of plant functional traits and the soil microbial activity in modulating C, N and GHG fluxes will be investigated in both field-based and controlled environment studies.

The results obtained will be disseminated to local stakeholders (primarily farmers and natural park authorities) and to the scientific community.