Tuesday, November 14, 2006

Effects of Mowing Height and Drought on Kentucky Bluegrass and a Hybrid Bluegrass.

Kemin Su, Dale Bremer, Steve Keeley, and Jack Fry. Kansas State University, 2021 Throckmorton Plant Sciences Ce, Manhattan, KS 66506, United States of America

Kentucky bluegrass (Poa pratensis L.) (KBG) is a cool-season turfgrass commonly used in the transition zone of the USA. Hybrid bluegrass (HBG), which is a genetic cross between native Texas bluegrass (Poa arachnifera Torr.) and KBG, has similar visual characteristics as KBG but may be more heat and drought tolerant. The objectives of this study were to investigate the performance of a KBG (‘Apollo’) and a HBG (‘Thermal Blue’) under different mowing heights and irrigation treatments. A field study was conducted for two years under a rainout shelter near Manhattan, KS, USA. Eight treatments included combinations of the two species at two different mowing heights (3.81 cm and 7.62 cm), and two irrigation levels (60% and 100% evapotranspiration replacement). The experimental design was arranged in a randomized complete block design with four replications. Evapotranspiration (ET) was calculated with the Penman-Monteith equation using climatological variables from a nearby weather station. Photosynthesis was measured biweekly on clear days between 1100 and 1500 CDT, with a LI-6400 portable gas exchange system. Visual quality was weekly rated. Volumetric soil water content (θv) at 5, 15, and 20 cm was measured using the dual-probe heat-pulse technique, and θv from 0 to 50 cm was measured by time domain reflectrometry. Drought stress (60% ET replacement) caused a decline in gross photosynthesis (Pg) and visual quality of both species. The lower mowing height reduced their Pg during both years and visual quality during the first year. Preliminary results indicated that KBG performed better than HBG.