Experiments done in Santander de Quilichao (Cauca, Colombia) on two cassava cultivars indicated that cassava had at least three defence mechanisms against water deficit, enabling it to assimilate and store photosynthates in roots, even during prolonged droughts. These mechanisms include partial stomatal closure, ability of leaves to maintain reasonable net photosynthetic rate for long periods of water stress, reduced leaf area, and exploration of water from deep soil layers. While cassava responded positively to fertilization, no significant statistical differences were found between treatments of stress and non-stress, confirming cassava's ability to tolerate soil water deficit.