STABILITY OF EVAPOTRANSPIRATION RATES IN KENTUCKY BLUEGRASS CULTIVARSACROSS LOW AND HIGH EVAPORATIVE ENVIRONMENTS

In an effort to conserve water applied to irrigated turfgrass sites, i t is important to assess the potential for water conservation among tu rfgrass germplasm. Turfgrass can respond differently in evapotranspira tion (ET) rate as climatic conditions change, The objective of this st udy was to investigate the interaction between the ET response of 61 K entucky bluegrass (Pen pratensis L., KBG) cultivars (evaluated under c ontrolled environment) and three equally spaced, evaporative environme nts (temperatures 25, 30, and 35 degrees C, corresponding to 1.263, 1. 664, and 2.261 kPa vapor pressure deficit, VPD, respectively), There w as a significant interaction (P less than or equal to 0.001) in ET rat e between the 61 cultivars and the three evaporative environments, Sim ple linear regression models and AMMI (additive main effect and multip licative interaction) models were used in interpreting cultivar-enviro nment interactions, There was wide variation in cultivar mean ET (5.36 -6.82 mm d(-1)), in stability of cultivar ET ranking, and sensitivity to evaporative environment characterized by cultivar stability, Cultiv ar stability (regression coefficients) varied by as much as 60% in the change in ET rate, from 1.13 to 3.16 mm d(-1) kPa(-1). The AMMI model revealed that the high evaporative environment (2.261 kPa VPD) intera cted with cultivars in a direction opposite to 1.263 and 1.661 kPa env ironments indicating that relative ET rankings of cultivars are the mo st variable between diverse evaporative environments. Compared with or dinary analysis of variance (ANOVA), AMMI was more effective in detect ing and interpreting interaction, This study indicated that (i) breedi ng for water conserving I(BG may have limited impact for reducing irri gation requirements because most of the variation in ET (87%) is due t o environment and not to the plant's pedigree, and (ii) recommendation s for use of specific cultivars may be difficult because of inconsiste nt water use patterns and intraspecies variation in KEG that were obse rved in response to diverse evaporative environments that are typical of field conditions.