Urea-ka: replacing inorganic nitrogen fertilizer with <i>Azolla pinnata</i> maintains rice yields with reduced input costs in the Senegal River Valley

Sustainability is essential for the creation of a secure, sufficient, and equitable global food supply and overreliance on expensive, synthetic fertilizers is a key challenge. Rice is a nitrogen-intensive crop, but Southeast Asian farmers are intercropping the nitrogen-fixing floating fern Azolla into rice paddies as a biofertilizer. However, despite its success and global distribution, Azolla is not widely used elsewhere. We assessed the feasibility of Azolla-rice intercropping in Saint-Louis, Senegal using a mixed-methods approach. We conducted interviews with farmers to assess their perceptions of Azolla-rice farming while they participated in an experiment to compare rice yields among four treatments: control plots (the existing practices of the farmer), Azolla plots (existing practices and adding fresh Azolla), low input plots (a 50% reduction of urea), and low input + Azolla plots (reduced urea + Azolla) in farmers’ paddies located in the Senegal River Valley. Across all five sites, there was a significant increase of 7.57% ± 4.62% SE (p-value = 0.05) in rice grain yield with Azolla additions. Replacing urea with Azolla caused a modest increase of 4.17% ± 4.61% SE (p-value = 0.18) in rice grain yield while reducing input costs by 33%. Our results suggest that Azolla-rice has high potential to improve productivity and livelihoods in Senegal.