FORAGES AND PASTURE MANAGEMENT Herbage Productivity and Botanical Composition of Hill Pasture as a Function of Clipping and Site Features

factors influencing the distribution of prairie species in complex terrain in central Canada (Lieffers and LarkinComplex topography and varied soil of hill-land pastures create Lieffers, 1987). Slope aspect also influenced diversity microsite conditions that support an array of floristic associations and herbage production patterns. This complicates management for forage of naturalized flora occurring at the site. Henderlong and livestock production because the seasonal distribution and quanet al. (1976) noted that the seasonal distribution of Kentity of forage vary. Our objective was to determine herbage production tucky bluegrass (Poa pratensis L.) herbage was affected and floristic composition of a hill pasture as a function of site characterby slope aspect. The distribution pattern was a function istics and canopy management. An existing 3-ha hill pasture watershed of plant response to growing conditions interacting with was oversown with white clover (Trifolium repens L.) and orchardthe microsite conditions created by topography. Producgrass (Dactylis glomerata L.) and fertilized with reactive phosphate tivity was also influenced by N application, and response (PO4 ) rock (PR). Replicated plots on each of four sites were clipped varied with slope aspect. Bluegrass yield was more than once (stockpiled), twice (hay harvest), or three times (long rotation) twofold greater on north-facing compared with southannually. Site had a significant impact on cumulative herbage producfacing slopes in northern West Virginia (Bennett et al., tion, whereas the influence of clipping was mixed. The least (1.9 Mg ha 1 ) amount of herbage production in a given season occurred on a 1976). northeast (NE)-facing site and the greatest (4.6 Mg ha 1 ) in a natural Deschenes (1966) found that aspect and slope infludrainage area (ND) traversing the pasture. Herbage production inence behavior of grazing livestock and concluded that creased by about 80% with overseeding and PR, but the relative rankmicrosite factors influencing temperature and soil water, ing of production among sites stayed the same. Botanical composition competitive interactions among species, and the influwas also strongly influenced by site, with velvetgrass (Holcus lanatus ence of grazing on plant competition and distribution of L.) predominating in ND and red fescue (Festuca rubra L.) occurring nutrients determined the species present. Topography primarily on the NE site. The stockpiled treatments became domiinfluenced grazing duration at a given site, where duranated by grasses and weeds 4 yr after treatments were imposed, regardtion decreased as slope steepness increased, and was less of site, and were similar to the least productive site (NE-facing) least on steep slopes with southern relative to northern in the pasture. Our results suggest that application of amendments to the more productive portions of a site are likely to have greater return. exposures. Aspect also influences when grazing begins, with north-facing slopes lagging behind south-facing slopes in central Appalachia (Stevens et al., 1976). Legumes in hill pasture increase N in the sward and T he high degree of spatial variability in hill-land pasimprove forage quality (Newbould, 1976). Bryan et al. ture creates a range of microsite conditions (Boyer (1987) observed that legume canopy cover, but not necet al., 1996; Radcliffe, 1982) that influence productivity essarily legume mass, was increased with P. Bryan et al. and botanical composition of plant communities (Baker, (1987) also noted that grazing management had a greater 1976). Slope aspect, for example, determines the amount influence on sward composition than lime or P. Conseof intercepted radiation (Radcliffe, 1982) and the direcquently, more intensive management approaches are tion and strength of air currents (Lambert and Roberts, desirable, such as managed grazing combined with prac1976). Exposure to solar radiation and wind results in tices that have long-lasting effects, including application widely varying potential evaporation (Feldhake and Boyof P and lime and N fixation from perennial legumes er, 1990), which interacts with soil catena to influence (Gillingham et al., 1998). However, evidence shows that transpiration, makeup of the floristic community, and these practices are not uniformly successful in hill-land herbage productivity. The influence of elevation and topsituations (Lambert et al., 1983, 1986). Steep terrain and ographic microsite on occurrence and distribution of economic constraints might restrict precision applicaspecies and vegetation is widely acknowledged and tion of soil amendments and seed mixtures. Microsite clearly presented in an example by Ayyad and Dix (1964), conditions including biophysical and floristic attributes but very few experiments document the effects for hillcould also influence renovation success. Our objective land pasture situations in the humid eastern USA. was to determine sward productivity and botanical comSlope position and aspect were the most important position as a function of clipping frequency on different sites in a seminatural hill pasture receiving a uniform USDA-ARS, Appalachian Farming Syst. Res. Cent., 1224 Airport application of phosphate rock (PR) and overseeding of Rd., Beaver, WV 25813. Received 18 Dec. 2000. *Corresponding author ([email protected]). Abbreviations: ND, natural drainage area; NE, northeast; NW, northwest; PR, phosphate rock; SW, southwest. Published in Agron. J. 94:351–358 (2002).