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Title: INFLUENCE OF MICROSITE SOLAR RADIATION CONDITIONS AND TIME ON NUTRITIVE VALUE OF COOL SEASON FORAGES IN A CONIFER WOODLOT

Author
item Neel, James - Jim
item Feldhake, Charles
item Belesky, David

Submitted to: American Forage and Grassland Council Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2004
Publication Date: 6/12/2004
Citation: Neel, J.P., Feldhake, C.M., Belesky, D.P. 2004. Influence of microsite solar radiation conditions and time on nutritive value of cool season forages in a conifer woodlot. Proceedings of American Forage and Grassland Council Conference. 13:474-478.

Interpretive Summary: The Appalachian region contains numerous small farms made up of both open pasture and woodlots. A common problem is the loss of forage quality and quantity during the summer period due to high temperature and low rainfall. Microsite conditions associated with woodlots offer promise of improved forage availability, higher forage quality and increased farm income. A grass-legume mixture was established under a light gradient created by a mixed-species conifer stand. Mature wether sheep were used to control existing under-story vegetation and to tread in surface broadcast seed. Herbage quality of the grazed sward was quantified as a function of light intensity and time. Our findings suggest theoretically high quality herbage can be produced under a conifer tree canopy, with varying available light intensities. Although herbage energy content would be considered good to high, the nitrogen to energy ratio is excessive and could impact animal performance or nutrient cycling within the grazing system. Low light availability reduces forage non-structural carbohydrate which may impact palatability. Herbage ash content was higher in low light areas and further investigation concerning mineral profiles is warranted. Information is needed on grazing management practices to determine how the simultaneous stresses of shade and defoliation influence herbage nutritive value, plant productivity and sward persistence.

Technical Abstract: The Appalachian region contains numerous small farms made up of both open pasture and woodlots. A common problem is the loss of forage quality and quantity during the summer period due to high temperature and low rainfall. Microsite conditions associated with woodlots offer promise of improved forage availability, higher forage quality and increased farm income. Nutritional value of herbage grown under a conifer tree canopy was evaluated in relation to available light and season. Forage crude protein was influenced by available light (P<0.001) and was highest (P<0.05) within the 50% available light area (24.9%) and lowest (P<0.05) within the 80% available light area (20.7). Forage metabolisable energy was also affected by light level (P<0.001) with energy content being greatest at 80% light availability. An interaction (P<0.05) between light level and harvest date with regards to nitrate content occurred but, nitrate content was lowest within the 80% treatment across all harvest dates. Total nonstructural carbohydrates (TNC) were highest (P<0.05) within the 80% light area (9.6%). Ash content was influenced (P<0.001) by available light. Nutritive value varied with season (P<0.001). Forage quality estimates suggest low light conditions may negatively impact nutritive value (e.g. forage TNC content).