Tiller production in cocksfoot (Dactylis glomerata) and tall fescue (Festuca arundinacea) growing along a light gradient

Authors: Belesky, David; Ruckle, Joyce; Burner, David

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2011
Publication Date: 8/1/2011
Citation: Belesky, D.P., Ruckle, J.M., Burner, D.M. 2011. Tiller production in cocksfoot (Dactylis glomerata) and tall fescue (Festuca arundinacea) growing along a light gradient. Grass and Forage Science. 66(3):370-380.

Interpretive Summary: Small farms in much of the eastern US are a mosaic of woodland and open pasture. Silvopastoral grazing systems, or forages produced as understory crops on wooded sites contribute to increased land-use efficiency and biological diversity on small farms. Orchardgrass and tall fescue, a common forage grasses in the central Appalachian region were grown in un-shaded pasture, woodlot and woodland-unshaded pasture edge (simulate varying shade conditions of selectively thinned tree stands) environments to determine how the production of tillers or vegetative propagules influenced productivity of the herbage. Shade-grown plants had fewer tillers, which could influence persistence and productivity of the plants and ultimately grazing livestock performance. Peak tiller production occurred at different times depending on where plants were growing and the intensity of clipping management. Plants growing in the shaded woodlot invested energy in extending leaves to improve the chances of capturing light at the expense of sustained persistence. Clipping placed additional stresses on the light capturing ability of the plants. Orchardgrass, but not tall fescue, sustained leaf and tiller production in the shaded sites including the relatively dense shade of the woodlot site, suggesting that orchardgrass tolerated shade and defoliation and was suited to silvopasture in a cool-temperate region.

Technical Abstract: Pasture managers seek to balance leaf appearance with leaf utilization to meet livestock nutritional needs and sustain sward productivity. Achieving this balance when managing forages in silvopasture, requires techniques that account for the influence of light and defoliation on tiller appearance and development. To that end, we determined the production of tillers as a function of light availability and residual clipping height of two widely used forage grasses adapted to the cool, humid temperate conditions of Appalachia in the eastern USA. Tiller production of orchardgrass and tall fescue was greatest in unshaded sites and least in shaded woodlot sites, irrespective of residual clipping height. Juvenile plants produced more than twice as many tillers as did mature plants, with this difference accentuated by site. This response reflected a shift in reproductive and resource use strategies and suggests that management techniques for newly sown stands differ from established swards. Trends in tiller production were: Benchmark orchardgrass > Max Q tall fescue; 10-cm > 5-cm residual clipping height; and unshaded > partially shaded > densely shaded sites. Tiller production peaked at different times during the growing season depending on species, sites and clipping management. Peaks occurred earlier in the year in the woodlot site for both species, regardless of residual clipping height, and later in the year at the unshaded site. Plants growing at the wooded site extended leaves quickly. While this sustained herbage production, it led to a weakened plant with less non-structural carbohydrate and fewer tillers. Orchardgrass, but not tall fescue, sustained leaf and tiller production in the shaded sites including the relatively dense shade of the woodlot site, suggesting that orchardgrass tolerated shade and defoliation in a cool-temperate region.