DACTYLIS GLOMERATA GROWING ALONG A LIGHT GRADIENT IN THE CENTRAL APPALACHIAN REGION OF THE EASTERN USA: III. NONSTRUCTURAL CARBOHYDRATES AND NUTRITIVE VALUE

Authors: Belesky, David; Chatterton, N; Neel, James

Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2005
Publication Date: 1/15/2006
Citation: Belesky, D.P., Neel, J.P., Chatterton, N.J. 2006. Dactylis glomerata growing along a light gradient in the central Appalachian region of the eastern USA: III. Nonstructural carbohydrates and nutritive value. Agroforestry Systems. 67:51-61.

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, a common forage grass in the central Appalachian region was grown in open, shaded and woodland-open edge (simulate varying shade conditions of selectively thinned tree stands) environments to determine productivity and nutritive value of the herbage. Shade-grown plants had less nonstructural carbohydrate and greater nitrogen concentrations, which could influence grazing livestock selectivity and performance. Results suggest that forage would not have enough energy and that nitrogen is present in excess in plant tissue. Shade-grown herbage use can be delayed somewhat during the growing season relative to open pasture, because fiber content is low and the typical advance in maturity and decline in herbage quality is slow. 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: Silvopastoral grazing systems can improve the seasonal and temporal distribution of herbage mass production. Microsite influences plant development and resource allocation in orchardgrass (Dactylis glomerata L.), a traditional pasture species with potential as an understory crop in woodlots in the humid eastern USA. 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 quantity and distribution of nonstructural carbohydrate and crude protein among plant parts of defoliated orchardgrass. Plants established in spring (SP) and late summer (LS) were clipped each time mean height reached 20 cm. Time of establishment and use of shade-grown orchardgrass had a major influence on nonstructural carbohydrate and protein content of herbage. There are some trade-offs in terms of nutritive value of shade-grown compared to open pasture herbage; increased protein content in shade-grown plants is offset by lower fiber, lower nonstructural carbohydrate and corresponding reduce preference. The ratio of C:N and thus herbage energy expressed as total digestible nutrients, relative to crude protein declined as shade increased. Use of herbage grown in partial shade can be delayed somewhat during the growing season relative to open pasture, because fiber content is low and the typical advance in maturity and decline in herbage quality is slow.