Although cassava can withstand periods of drought, it is very sensitive to soil water deficit during the first three months after planting. Water stress at any time in that early period reduces significantly the growth of roots and shoots, and impairs subsequent development of the storage roots.
Once established, cassava can grow in areas that receive just 400 mm of average annual rainfall. But higher yields have been obtained with much higher levels of water supply. Research in Thailand indicates that maximum root yields are correlated with rainfall totalling about 1 700 mm during the fourth to eleventh month after planting. Cassava also responds well to irrigation. In trials in Nigeria, root yields increased sixfold when the quantity of water supplied by supplementary drip irrigation matched that of the season’s rainfall.