Influence of Solar Radiation on the Productivity and Nutritive Value of Herbage of Cool-Season Species of an Understory Sward in a Mature Conifer Woodland

Authors: Neel, James; Feldhake, Charles; Belesky, David

Submitted to: Grass and Forage Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2007
Publication Date: 2/14/2008
Citation: Neel, J.P., Feldhake, C.M., Belesky, D.P. 2008. Influence of Solar Radiation on the Productivity and Nutritive Value of Herbage of Cool-Season Species of an Understory Sward in a Mature Conifer Woodland. Grass and Forage Science. 63(1):38-47.

Interpretive Summary: The Appalachian region has many small-scale, pasture-based livestock farms that are a mosaic of open pasture and woodland. Silvopastoral systems would increase carrying capacity and may help ensure a reliable supply of high quality herbage. An experiment was conducted to evaluate the influence of shade and growing season on nutritive value of a mixture of sown grasses and legumes established by low input means under a stand of mixed species pine trees. When forage energy in relation to nitrogen is considered, all treatments produced herbage containing excess nitrogen from both an animal and rumen micro-flora standpoint. Herbage energy:nitrogen should be given strong consideration in the development of silvo-pastoral management decisions. Our findings suggest high levels of shade are associated with the production of undesirable herbage relative to the nutritional needs of grazing livestock, especially if utilized as the sole forage source. Excess herbage nitrogen may negatively impact the environment. However, high nitrogen levels indicate that silvopasture could be utilized as a protein supplement to low nitrogen and energy containing pasture.

Technical Abstract: The Appalachian region has many small-scale, pasture-based livestock farms that are a mosaic of open pasture and woodland. Silvopastoral systems would increase carrying capacity and may help ensure a reliable supply of high quality herbage. An experiment was conducted to evaluate the influence of solar radiation (20, 50 or 80 % of maximum solar radiation; 20-, 50- and 80-MSR respectively) and growing season (early, mid and late; E, M and L respectively) on botanical composition and nutritive value of a mixture of sown grasses and legumes established by low input means under a stand of conifers (mixed species). Introduced forage species increased as a percent of sward from 2000 to 2002. Crude protein (CP) content of herbage was 20% or greater except for E 80-MSR during 2001. Herbage nitrate levels were such that intake would need to be limited 83% of the time within 20- and 50-MSR. Herbage from 80-MSR had greater total nonstructural carbohydrate (TNC) content compared to 20- and 50-MSR during all three years. Estimated energy content of herbage, as total digestible nutrients (TDN), was similar across all treatments. When energy in relation to nitrogen (TDN:CP) is considered, all treatments produced herbage containing excess nitrogen from both an animal and rumen micro-flora standpoint. Our findings suggest low levels of solar radiation are associated with the production of undesirable herbage relative to the nutritional needs of grazing livestock. High CP levels indicate that silvopasture could be utilized as a protein supplement to low nitrogen, higher fiber herbage.