Describing the Botanical Composition of a Mixed Species Northeastern U.S. Pasture Rotationally Grazed by Cattle

Abstract

Pastures in the northeastern USA typically contain multiple species with different plant morphologies and seasonal growth. We hypothesized that some measures of botanical composition do not describe the contribution of species to forage for grazing animals, knowledge that is necessary to improve animal production. We compared three measures of botanical composition: (i) harvested herbage at prescribed post‐grazing heights, (ii) total herbage cut at ground level, and (iii) tiller/leaf density. In spring, summer, and fall 1998 to 2000, we sampled a mixed pasture of orchardgrass (Dactylis glomerata L.), bluegrass (Poa sp. L.), quackgrass [Elytrigia repens (L.) Nevski], legumes, and other species that was rotationally grazed by cattle. We measured ground cover in 1999 and 2000. Relative ranking and percent contribution of orchardgrass, bluegrass, white clover (Trifolium repens L.), tall legumes, and other species differed significantly among methods; only dandelion (Taraxacum officinale Weber in Wiggers) and quackgrass measures did not. Percentage of harvested herbage from orchardgrass, tall legumes, and other species was greater than percentages based on total herbage, ground cover, and tiller/leaf density. More prostrate and shorter‐growing bluegrass and white clover contributed smaller percentages to harvested herbage than to the other botanical composition measures. Interaction of botanical composition measure by season was significant for white clover and other species; bluegrass, quackgrass, and white clover percent contribution to the sward differed with season. To improve an understanding of the relative contribution of species to grazed forage in a mixed pasture, and to enhance animal production, harvested herbage should be measured rather than total herbage, ground cover, or tiller/leaf density; and preferably during spring, summer, and fall.