Stability of Evapotranspiration Rates in Kentucky Bluegrass Cultivars across Low and High Evaporative Environments

Abstract

In an effort to conserve water applied to irrigated turfgrass sites, it is important to assess the potential for water conservation among turfgrass germplasm. Turfgrass can respond differently in evapotranspiration (ET) rate as climatic conditions change. The objective of this study was to investigate the interaction between the ET response of 61 Kentucky bluegrass (Poa pratensis L., KBG) cultivars (evaluated under controlled environment) and three equally spaced, evaporative environments (temperatures 25, 30, and 35°C, corresponding to 1.263, 1.664, and 2.261 kPa vapor pressure deficit, VPD, respectively). There was a significant interaction (P ≤ 0.001) in ET rate between the 61 cultivars and the three evaporative environments. Simple linear regression models and AMMI (additive main effect and multiplicative interaction) models were used in interpreting cultivar‐environment 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. Cultivar stability (regression coefficients) varied by as much as 60% in the change 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) interacted with cultivars in a direction opposite to 1.263 and 1.664 kPa environments indicating that relative ET rankings of cultivars are the most variable between diverse evaporative environments. Compared with ordinary analysis of variance (ANOVA), AMMI was more effective in detecting and interpreting interaction. This study indicated that (i) breeding for water conserving KBG may have limited impact for reducing irrigation requirements because most of the variation in ET (87%) is due to environment and not to the plant's pedigree, and (it) recommendations for use of specific cultivars maybe difficult because of inconsistent water use patterns and intraspecies variation in KBG that were observed in response to diverse evaporative environments that are typical of field conditions.