COMPARING TURFGRASS CUMULATIVE EVAPOTRANSPIRATION CURVES

Twenty-rive 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.