ABSTRACT The objective of this study was to propose a model, named Simanihot, for simulating growth, development and yield of tuberous roots in cassava, with a choice of two soil water balance models. The model works on a day time step and is calibrated for five cassava cultivars (Fepagro –RS 14, Estrangeira, Cascuda, São José e Paraguaia), with different branching habits and different purpose of use (pasture, food and industry). The model has a graphical interface, where the user can choose one out of two soil water balance models, depending upon the number of known soil variables and details the user wants to know about soil water content.