Forage production of tropical grasses under extended daylength at subtropical and tropical latitudes

Decreased growth of warm-season forage grasses during subtropical winters has been shown to be a response to short-daylength during those months. The objective of this research was to evaluate the influence of short-daylength on growth of forage grasses in low latitude locations. Three grasses (Argentine bahiagrass, Paspalum notatum Flügge; Common guineagrass, Panicum maximum Jacq.; Tifton-85 bermudagrass, Cynodon spp. Pers.) were grown at three locations (south Florida, Puerto Rico, and St. Croix) under extended (15 h) and natural daylength during 2 years. Plots were harvested at 5-week (October-February) and 4-week (March-April) intervals to measure dry matter (DM) yield and nutritive value of the herbage. Daylength effects were found on DM harvested for all grasses in south Florida (P < 0.01). At that location, grasses exposed to increased daylength averaged a 44% increase in DM harvested compared to those grown under natural daylength. Daylength effects were consistent for bahiagrass at the other two locations as well. However, guineagrass and bermudagrass did not respond to extended daylength in Puerto Rico and St. Croix. These results showed that bahiagrass is capable of producing additional forage during the cool season at all locations tested if sensitivity to photoperiod is genetically removed or attenuated.