Ala et al. (2008) have proposed a soil ionization model, on the basis of the dynamic soil-resistivity model of Liew and Darveniza (1974), for finite-difference time-domain (FDTD) computations, and tested the validity of the model against experiments on a single vertical grounding rod. In the model, the resistivity of each soil-representing cell is controlled by the instantaneous value of the electric field there and time. In this paper, in order to test the validity of this model, it has been applied to analyzing the surge response of a 0.6-m long single vertical grounding rod connected to four auxiliary vertical conductors, buried in a homogeneous soil. The FDTD-computed response agrees reasonably well with the corresponding measured one. Also, influences of parameters of the soil ionization model have been studied.