Two-year field trials were conducted under prolonged early water stress (occurring 2 - 6 months after planting); mid-season stress (4 - 8 months after planting), and ter- minal (i.e., end-of-season) stress (6 - 12 months after planting). Table 3 presents data on root yield, shoot and total biomass at 12 months, and nutrient use efficiency in terms of root production. On one hand, water stress re- duced shoot biomass in all stages but reduction was sig- nificant only in early stress. On the other hand, final root yield across clones was not significantly reduced at any water shortage treatment. However, at the end of early and mid-season stress both shoot and storage root were significantly reduced, but recovered after release from stress. This response demonstrates the resilience of cas-sava and its adaptability to prolonged water stress