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Production Papers

Regrowth Interval Influences Productivity, Botanical Composition, and Nutritive Value of Old World Bluestem and Perennial Ryegrass Swards

USDA-ARS, Appalachian Farming Systems Research Center, 1224 Airport Road, Beaver, West Virginia 25813

^* Corresponding author (david.belesky{at}ars.usda.gov)

Received for publication April 5, 2005. Botanical composition of pasture in much of the Appalachian Region varies as weather patterns interacting with abiotic and biotic factors create conditions allowing a range of plant species to occupy temporal and spatial gaps in the stand. Field-grown old world bluestem [Bothriochloa caucasia (Trin.) C.E. Hubb.] or perennial ryegrass (Lolium perenne L.) were defoliated at fixed time intervals (1-, 2-, or 4-wk for old world bluestem and 2-, 4-, or 6-wk intervals for perennial ryegrass). Herbage mass, sward botanical composition, and estimates of nutritive value were determined. White clover (Trifolium repens L.), black medic (Medicago lupulina L), and various common forbs and grasses volunteered in all stands. Old world bluestem yields ranged from 3.38 Mg ha^–1 (1-wk regrowth interval in 2002) to 9.42 Mg ha^–1 (4-wk regrowth interval in 2000). Perennial ryegrass yield increased with increasing regrowth interval in 2002, ranging from 3.16 to 7.29 Mg ha^–1. The longest regrowth interval did not necessarily lead to the greatest productivity. Old world bluestem swards clipped at 4-wk intervals decreased 60% by the third growing season, whereas perennial ryegrass swards clipped at 6-wk intervals increased by 37%. The proportion of encroaching species increased substantially in perennial ryegrass but not old world bluestem swards by 2002, suggesting that combined effects of repeated defoliation and weather influenced sward composition and productivity. Choice of plant resource, timing and intensity of defoliation, and very likely nutrient inputs coinciding with requirements of sown species could influence sward composition and help manage diversity to sustain productivity.