Why has small-scale irrigation not responded to expectations with traditional subsistence farmers along the Senegal River in Mauritania?

► We surveyed subsistence households along the Senegal River Valley in Mauritania. ► Traditional cropping does not provide sufficient human digestible energy. ► There is no shortage of labor when irrigated rice is combined with traditional cropping. ► There is a negative return of rice production to labor and inputs. ► Rice negative returns explains observed gradual abandonment of irrigation schemes.