ESTIMATING TURFGRASS EVAPOTRANSPIRATION USING ATMOMETERS AND THE PENMAN-MONTEITH MODEL

Information is lacking on the precision of atmometers and empirical mo dels used to estimate turfgrass evapotranspiration (ET). Experiments w ere conducted to evaluate the precision of black Bellani plates, a cla ss A evaporation pan, and the Penman-Monteith empirical model for esti mating ET of 'Mustang' tall fescue (Festuca arundinacea Schreb.), 'Mey er' zoysiagrass (Zoysia japonica Steud.), 'Prairie' buffalograss [Buch loe dactyloides (Nutt.) Engelm.], and 'Midlawn' bermudagrass [Cynodon dactylon (L.) Pers. x transvaalensis Burtt-Davy] under well-watered co nditions. Tall fescue was mowed once weekly at 6.5 cm, and warm-season grasses were mowed at 4.5 cm twice weekly. Diurnal ET was measured be tween June and September in 1993 and 1994 using weighing lysimeters an d the water balance method. Evaporation from atmometers was measured d uring the hour that turfgrass ET was determined, and Penman-Monteith-e stimated ET was calculated for the same time period. Black Bellani pla te evaporation was correlated most closely with measured turf ET (R(2) = 0.73), followed by class A pan evaporation (R(2) = 0.67), and Penma n-Monteith-estimated ET (R(2) = 0.60). Ranking of grasses for mean dai ly ET was tall fescue (6.8 mm d(-1)) > zoysiagrass (5.6 mm d(-1)) > bu ffalograss (5.1 mm d(-1)) = bermudagrass (5.0 mm d(-1)). The black Bel lani plate provides the most precise estimate of turfgrass ET under we ll-watered conditions.