Forage Yield of Smooth Bromegrass Collections from Rural Cemeteries

limited by the timing of new tiller development. Development of new tillers in smooth bromegrass is largely Smooth bromegrass (Bromus inermis Leyss) is poorly adapted to determinant, with synchronized elevation and elongamanagement-intensive rotational grazing because of slow and limited tion of new apical meristems above the soil surface regrowth potential. In an effort to discover germplasm with tolerance to frequent cutting, smooth bromegrass plants were collected from (Krause and Moser, 1977). Regrowth is reduced by cutfence and sod habitats of 30 rural cemeteries in Iowa, Minnesota, and ting or grazing before new tillers have developed suffiWisconsin. The objective of this study was to quantify, describe, and ciently, eventually reducing persistence (Eastin et al., test the responses of paired fence and sod populations to different 1964; Reynolds and Smith, 1962). During reproductive harvest frequencies. Thirty sod populations, 30 fence populations, development, this critical time occurs from culm elongaand five cultivars were evaluated for season-total forage yield and tion to late heading. Cutting before culm elongation (to regrowth percentage at Arlington, WI, and Ames, IA. Three harvest avoid removal of apical meristems) or well after heading managements were used, with mean harvest frequencies of four, five, (when new tillers have begun to emerge) leads to inor six harvests over 2002 and 2003. Fence populations had an average creased forage yields and persistence (McElgunn et al., forage yield 5.5% higher than sod populations, a difference that was fairly consistent across harvest managements, test locations, and state 1972; Paulsen and Smith, 1968). Apical dominance in of origin. Variation in linear responses to harvest management made smooth bromegrass is strong until anthesis, when auxin up 65 and 77% of the harvest management population interaction activity declines and tillering is normally resumed (Eastin for forage yield and regrowth percentage, respectively. For seven et al., 1964). Because smooth bromegrass produces true cemetery sites, the sod population was better adapted than the fence culms with elevated apical meristems on regrowth, timing population to a more frequent harvest management, as measured by of subsequent harvests may also be critical for smooth a more stable response to harvest frequency ( 2.02 0.10 vs. 2.67 bromegrass regrowth and persistence. Regrowth of smooth 0.12 Mg ha 1 harvest 1). For nine cemetery sites, the sod population bromegrass is not closely related to carbohydrate rehad a higher increase in regrowth percentage with increased harvest serves in roots and crowns (Eastin et al., 1964; Paulsen frequency (15.8 0.5 vs. 11.9 0.7% units harvest 1). Smooth bromegrass germplasm from some cemetery sods appears to have potential and Smith, 1969; Raese and Decker, 1966; Reynolds value for developing tolerance to frequent defoliation. and Smith, 1962). The first widespread use of smooth bromegrass in the USA occurred during the drought of the 1930s when it S bromegrass is an important forage grass in was an important component of hay, pasture, and consermuch of temperate North America, used primarily vation plantings (Casler and Carlson, 1995). Remnants for infrequent hay harvests, soil conservation, or other of these plantings can be found in rural areas throughout situations that are characterized by relatively low levels the central USA. Smooth bromegrass can persist in the of management. It is preferentially adapted to hay mansoil in the form of seed or rhizomes, potentially leading agement and favored by infrequent cutting, relatively to long-term persistence of remnant populations from high cutting heights, and high nitrogen fertility (Casler and plantings made in the 1930s. Carlson, 1995). Smooth bromegrass is not well adapted to Rural cemeteries are another source of smooth bromefrequent defoliation (Casler et al., 1998; Smith et al., grass germplasm that likely occurs as remnants of plant1973). Unlike many other cool-season forage grasses, ings from the 1930s. Many rural cemeteries of the North forage production of smooth bromegrass is not stimuCentral USA are characterized by a Kentucky bluegrass lated by defoliation, regardless of the growth stage (Har(Poa pratensis L.) sod that is well maintained by memrison and Romo, 1994; Lawrence and Ashford, 1969). bers of a local church or cemetery association. Smooth Smooth bromegrass stands decline under rotational bromegrass often survives in both the cemetery sod and grazing, an effect that is magnified by increasingly intenthe area surrounding the cemetery. In many cases, the sive grazing (Bittman and McCartney, 1994). fence or border population of smooth bromegrass is Regrowth and persistence of smooth bromegrass is unmanaged, creating two visually distinct habitats for smooth bromegrass: a frequently mowed sod and an uncut fence or border area. When compared in a comMichael D. Casler, USDA-ARS, U.S. Dairy Forage Research Center, mon nursery, fence and sod populations from many Madison, WI 53706-1108; E.C. Brummer, Dep. of Agronomy, Iowa cemeteries are phenotypically similar to each other, sugState Univ., Ames, IA 50010. This research was partially supported by the College of Agricultural and Life Sciences, Univ. of Wisconsin gesting that they represent a single population that has and the Raymond F. Baker Center for Plant Breeding at Iowa State not been modified by habitat management (Casler, Univ. Received 4 Feb. 2005. *Corresponding author (mdcasler@ 2004). Migration from the fence to the sod, either by wisc.edu). rhizomes or seed, may also contribute to maintenance Published in Crop Sci. 45:2510–2516 (2005). of genotypic diversity, but a similar overall phenotype Plant Genetic Resources in fence and sod populations. In other cases, there is doi:10.2135/cropsci2005.0116 clear phenotypic divergence between fence and sod pop© Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA ulations, suggesting the possibility that natural selection 2510 Published online October 27, 2005