This study examined the mechanical behavior of soils reinforced with Bahia grass roots under different shear displacements with two different models. The simple assessment method (Wu et al., 1979) assumes simultaneous breakage in vertical roots while the root strength model (Waldron and Dakessian 1981) assumes sequential breakage of vertical roots. Results indicate an underestimation of the shear strength increment of the soil among dense cluster roots when solely considering vertical roots and ignoring the contribution of lateral fine roots to soil reinforcement. On the contrary, the shear strength increment of the soil in sparse roots was overestimated with the assumption that the root.s mechanical behavior is characterized by simultaneous root breakage as proposed in the simple assessment formula. Compared with the simple assessment formula, the root strength model gives a more accurate estimation of value and its procedure is more realistic for understanding the mechanics of soil-root systems.