Author
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Belesky, David |
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Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/4/2004 Publication Date: 1/18/2005 Citation: Belesky, D.P. 2005. Growth of dactylis glomerata along a light gradient in the central appalachian region of the eastern usa: i. dry matter production and partitioning. Agroforestry Systems 65:81-90. 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 can increase land-use efficiency and biological diversity on small farms. Widely accepted management practices that link grazing management to forage height may not be applicable in the shaded component of silvopastoral systems because the influence of conditions within the shaded sites on response of defoliated plants are not well understood. Orchardgrass, a common forage grass in the central Appalachian region was grown in open, shaded and woodland-open edge environments to determine production patterns and persistence. Plants growing at the edge of wooded and open sites seemed to benefit from partial shade. Plants grown in the open experienced too much light and water stress whereas plants grown at the wooded sites had too little light to sustain regrowth of clipped plants. Clipping plants based on criteria to optimize grazing animal performance on open pasture was not suitable for shade grown plants. Understanding how to manage forage plants adapted to open pasture when grown in shade can lead to improved forage availability and distribution across a growing season, greater persistence and quite likely increased farm income. Technical Abstract: Traditional pasture species managed according to canopy development criteria may not respond the same when grown in the understory of woodlots because of microsite influences on development and resource allocation. Precise management criteria for silvopastoral swards are unknown. An experiment using container-grown plants was conducted under field conditions to determine how microsite of open (O), shaded woodland (W) and open-to-shaded woodland transition zones (EO, EW) influenced productivity and dry matter allocation in orchardgrass (Dactylis glomerata L.). Plants established in spring (SP) and late summer (LS) were clipped each time mean sward height reached 20 cm. Dry matter production differed between SP and LS plants, and decreased as light attenuation increased. Dry matter allocation indicated that some agronomic benefit in terms of allocation to leaf was obtained by growing plants in the EO and EW sites. Leaf mass did not vary with irradiance but stembase mass did. The SP plants had numerous small tillers whereas LS plants had fewer but more massive tillers. Plants growing at O, EO and EW were similar, whereas plants in the W site were smaller and had the fewest tillers regardless of planting time. Results suggest that defoliation management in shaded components of silvopastoral systems should be based on some index other than sward height, and that management criteria might change across a growing season. Less intensive removal (e.g., 10-cm rather that 5-cm residue) allows more of the meristem and nonstructural carbohydrate storage tissues to remain and may be appropriate for shade grown plants. |
