NERICAs (New Rice for Africa), new genotypes produced from the interspecific hybridization of Oryza sativa and O. glaberrima, have been bred in an attempt to improve the yield potential of rice cultivars adapted to resource-limited conditions in Africa. Identification of physiological traits responsible for their high-yielding potential under such conditions should be useful for rice-breeding programs to be employed not only in Africa but in other regions where rice production is being undertaken under low input conditions. In a series of experiments, we evaluated the growth and yield performance of upland NERICAs under rain-fed upland conditions with two levels of nitrogen application in comparison with Japanese elite rice cultivars, and attempted to identify the physiological traits responsible for the superior yield, if any. The upland NERICAs (NERICA 1 and NERICA 5) exhibited greater biomass production and yield than Japanese cultivars. The NERICAs also showed a higher rate of transpiration and exudation during the ripening stage, compared with elite Japanese cultivars. These results suggested that the greater water uptake ability of NERICAs appeared to be associated with their high N uptake capability, leading to greater biomass production and yield under water- and N-limited ecosystems. Further studies are needed to identify the specific root morphology involved in the water uptake ability of NERICAs.