Effect of Temperature, Daylength, and Solar Radiation on Production of Coastal Bermudagrass

Forage yields of ‘Coastal’ bermudagrass [ Cynodon dactylon (L.) Pers.] drop sharply in late summer and fall, even though warm temperatures continue. The objective of this study was to examine relationships among meteorological parameters and forage yield of irrigated and rain‐fed Coastal bermudagrass fertilized annually with 672 kg ha −‐1 of N plus adequate P and K. Irrigation maintained soil water pressure above –25 kPa, as indicated by gypsum blocks. Forage from six irrigated and six rain‐fed plots was harvested at eight 24 d intervals. Three‐year average yields for the eight growth periods ranged from 295 kg ha −1 in October to 2907 kg ha −1 in June. Stepwise multiple regression of yields from individual cuttings with various meteorological parameters indicated that daylength was the single most important variable related to yield ( r 2 =0.64). Total rainfall plus irrigation, mean minimum temperature, growing degree days, and mean daily solar radiation could be associated with yield to a limited extent. Over years, yield was most highly correlated with daylength and solar radiation, ( r =0.95 and 0.93, respectively,) indicating that these factors were largely responsible for low yields of Coastal bermudagrass forage in the fall. The small correlation between average yields and average temperatures ( r =0.46) or average growing degree days ( r =0.37) for the eight 24‐d growth periods resulted from the failure of Coastal bermudagrass to grow well in the fall even when water, fertilizer, and temperature were adequate.