Herbage Accumulation of Three Bahiagrass Populations during the Cool Season

to regional environmental conditions. Bahiagrass is particularly tolerant of poor soil drainage, close continuous Fall and winter are periods of critical forage shortage in subtropical grazing, and marginal fertility. regions of the world, including the extreme southeastern USA. CoolBeginning in 1960, Burton (1974, 1982) used modified season herbage accumulation has not been documented for bahiagrass [Paspalum notatum Flügge var. saurae Parodi] that has been selected mass selection (RRPS) to develop improved bahiagrass using recurrent restricted phenotypic selection (RRPS) for increased populations from the diploid cultivar Pensacola. Tifton warm-season yield. Regrowth of ‘Pensacola’, ‘Tifton 9’, and RRPS 9, resulting from nine cycles of RRPS, is higher yielding Cycle 18 that accumulated for 15 or 30 d was harvested from midthan Pensacola and was released in 1987 (Burton, 1989). September through mid-April at Tifton, GA and Ona, FL for 2 yr. Eighteen cycles of RRPS breeding resulted in the experHerbage accumulation was essentially parallel for the three populaimental population RRPS Cycle 18, which is higher tions; minimums were coincident in midwinter, and maxima generally yielding than both Pensacola and Tifton 9 (Burton et occurred at the first autumn harvest or last spring harvest. Fall and al., 1997). Increased spring herbage accumulation was spring yields of Tifton 9 and RRPS Cycle 18 were generally higher the basis for the selection of Tifton 9 and RRPS Cycle than those of Pensacola and often more than double. This advantage 18 (Burton, 1974, 1982, 1989), and yield advantages durwas more pronounced at Ona than Tifton. Digestibility (600 g kg21) ing the typical growing season have been demonstrated and crude protein (CP) concentration (150 g kg21) at Ona remained high throughout the cool season. However, forage quality of (Pedreira and Brown, 1996; Burton et al., 1997; Gates bahiagrass at Tifton tended to decrease with increased frosts. Coolet al., 1999). One possible approach to reduce the critical season growth of three bahiagrass populations was slow, but RRPS forage deficits occurring from fall through spring is to selection has led to populations with greater growth potential, except identify bahiagrass populations that are more producwhen cold temperatures prohibit growth entirely. tive under cool temperatures. Previous research has demonstrated that bahiagrass makes 86% of its growth during the six warmest months W perennial grasses, particularly berof the year, even in peninsular Florida (Beaty et al., mudagrass [Cynodon dactylon (L.) Pers.] and 1980; Mislevy and Everett, 1981). However, the duration bahiagrass, provide the feed supply base for cow calf of the period of active growth has not been thoroughly production in the lower South. These forages provide examined. Previous observations indicate the improved abundant feed of adequate nutritional value from late cultivar Tifton 9 accumulated 30% more forage during spring through early autumn. This predictable seasonal winter than Pensacola (Mislevy et al., 1990). It is not distribution of growth leads to equally predictable periknown if selection for increased yield has simply inods of feed shortage that are often most critical in late creased herbage accumulation at all temperatures, or if fall and early winter. Feed supplies must be supplean increase occurred above some temperature threshmented with hay, concentrates, or cool-season annual old. An evaluation of the cool-season production of forages when warm-season grasses are not actively recently developed bahiagrass cultivars and populations growing. Mean daily temperatures during autumn, winwith the potential for greater total herbage growth is ter, and early spring range between about 9 and 268C a logical starting point to increase cool-season bahiaand are adequate to support the growth of cool-season grass production. species. Bermudagrass is dormant during winter, followResearch was conducted to monitor the distribution ing freezing temperatures. Bahiagrass, in contrast, can of growth during the cool months (Oct.–Mar.) of the remain green, especially at winter temperatures .08C. year for three diverse bahiagrass populations: PensaAlthough Pensacola bahiagrass was not introduced cola, Tifton 9, and RRPS Cycle 18. The objectives were into North America until 1936 (Burton, 1967), its wideto quantify the herbage accumulation and forage quality spread proliferation throughout the lower southeastern of aboveground biomass. USA demonstrates excellent adaptation by this species MATERIALS AND METHODS R.N. Gates, USDA-ARS, Crop Genet. and Breeding Res. Unit, This field study was conducted during the fall and winter Coastal Plain Exp. Stn., Tifton, GA 31793; P. Mislevy, Univ. of Floriof 1993–1994 and 1994–1995 at the Coastal Plain Experiment da, Inst. of Food and Agric. Sci., Range Cattle Res. and Educ. Station, Tifton, GA (318269 N, 838359 W) on Alapaha sand Cent., Ona, FL 33865; and F.G. Martin, Inst. of Food and Agric. Sci., Dep. of Statistics, Univ. of Florida, Gainesville, FL 32611-0339. Received 3 Feb. 2000. *Corresponding author ([email protected]. Abbreviations: CP, crude protein; IVDMD, in vitro dry matter disappeachnet.edu). pearance; IVOMD, in vitro organic matter disappearance; RRPS, recurrent restricted phenotypic selection. Published in Agron. J. 93:112–117 (2001). GATES ET AL.: HERBAGE ACCUMULATION OF BAHIAGRASS DURING THE COOL SEASON 113 Table 1. Stage, harvest, and midpoint date and duration of regrowth intervals for three bahiagrass entries grown at Tifton, GA and Ona, FL during the 1993–1994 and 1994–1995 seasons.