Every year, large amounts of nitrogen fertilisers are used around the world to sustain the cultivation of rice. The wetland culture conditions required for rice cause nitrogen to leach and contaminate freshwater, triggering a number of adverse consequences for aquatic habitats. Dr Consolación Álvarez and Dr Vicente Mariscal Romero, from the Spanish National Research Council (CSIC), Spain, propose the development of new rice biofertilisers based on nitrogen-fixing cyanobacteria. The stable plant-cyanobacteria symbiosis can be exploited in rice crops to stimulate plant growth in the absence of synthetic nitrogen fertilisers.