Fig. 1. AMMI-1 plot of 69 environments (location-year combinations) from the 1990 NTEP Kentucky bluegrass variety trial and 60 environments from the 1990 perennial ryegrass variety trial. IAS-1 = interaction scores for the first interaction axis, IAS-1 scores close to zero indicate little or no interaction (IAS-1 scale in units equivalent to the square root of turfgrass quality). Displacement along the vertical axis indicates interaction differences between environment. Displacement along the horizontal axis indicates differences in environment main effects. Dash lines show year-to-year variation within individual locations.