Basal growth temperatures and growth rate constants of warm-season turfgrass species

Degree-day modeling applications in turfgrass management have recently seen increased interest. The predictive capacity of any degree-day model is dependent on an accurate determination of the basal growth temperatures for the species under consideration. The objective of this study was to determine basal growth temperatures and growth rate constants for eight warm season turfgrasses (five species). Sprigs from bermudagrass [Cynodon dactylon (L.) Pers. cv. Arizona Common and C. dactylon lc C. transvaalensis Burtt Davey cv. Midiron], buffalograss [Buchloe dactyloides (Nutt.) Engelm. cv. Kansas Common and Texoka], zoysiagrass (Zoysia japonica Steudel cv. Meyer), St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze cv. Raleigh and Floratam], and centipedegrass [Eremochloa ophiuroides (Munro) Hackel, cv. Common] were grown at temperatures ranging from 5 to 30°C in a controlled environment chamber under 14-h photoperiods. Chamber temperature was decreased in a step-wise fashion to the next temperature after two leaves were fully expanded. Leaf growth rates at each temperature were calculated and expressed as millimeters per day. Base temperature and growth rate constants for each turf grass were calculated with segmented nonlinear regression analysis. Base temperatures for the eight tested cultivars ranged from 0 to 13°C. Interspecific and intraspecific differences for basal growth temperature were found, indicating that degree-day model application accuracy is dependent on proper determination of target species and cultivar basal growth temperature.