Light Measurement Methods Related to Forage Yield in a Grazed Northern Conifer Silvopasture in the Appalachian Region of Eastern USA

Abstract

The Appalachian region is characterized by hilly topography and a humid temperate climate. In most areas agriculture is limited to pasture although the native climax vegetation is a species-diverse forest. Silvopasture systems can help diversify and increase farm income. Information is needed on the yield response of forage grown as an understory crop among trees. The light environment of a conifer silvopasture was characterized by three methods, a hand-held photosynthetically active radiation (PAR) meter for quick measurements over a large area, fixed PAR meters recorded using data loggers for a large number of measurements over time, and hemispherical photography with software to calculate seasonal direct beam radiation. Light data were considered in terms of forage yield. Plots were harvested when forage reached 20–25 cm in height after which the entire area was grazed by sheep. There were limitations to all methods of quantifying radiation environment for predicting yield. Yield decreased linearly with decreased PAR; however, data variability was high and correlations, while statistically significant, were weak. Grazed silvopastures are dynamic with shifting yield patterns in response to the interactions between the spatially variable soil, changing seasonal environment, and spatially variable animal impacts for each grazing event.