Tiller appearance, death and survival rates determine the persistence of each grass species and its herbage accu-mulation. The balance between these factors may vary with frequency and intensity of grazing and nitrogen (N) fertilization. Separate analysis of data on tiller appear-ance and survival or death may not indicate if tiller population is stable over a given time, that is, if suffi-cient tillers appear to replace those which die, keeping tiller population stable. Rather, an integrated analysis of tiller appearance and death is available, the tiller popula-tion stability index (SI), as defined by Bahmani et al