Comparing Turfgrass Cumulative Evapotranspiration Curves

Abstract

Twenty-five commercially available turfgrass cultivars were evaluated for cumulative evapotranspiration (ET cum ) attributes under progressive water stress for 0 to 21 and 0 to 24 days using the gravimetric mass balance method in two greenhouse studies. At the end of the water-stress treatment, the cultivars were scored visually for their green appearance on a 0 (no green) to 10 (100% green) scale. The Gompertz nonlinear model gave a best fit to ET cum vs. days adjusted for pan evaporation variation in the greenhouse compared with monomolecular and logistic nonlinear regression models. Two ET cum attributes—maximum evapotranspiration rates (ET max ) and inflection time (t i ) (the time when the change in ET becomes zero)—were estimated for each cultivar using the Gompertz model. Based on final ET cum , ET max , t i , and greenness score, `Bristol', `Challenger', and `Wabash' Kentucky bluegrass (Poa pratensis L.); `Shademaster' creeping fescue (Festuca rubra L.); `FRT-30149' fine fescue (F. rubra L.); and `Aurora' hard fescue (F. ovina var. duriuscula L. Koch.) were identified as low water-use cultivars.