Light Interception by Pasture Canopies as Affected by Height and Botanical Composition

Light interception (LI) by growing plants is essential for photosynthesis and growth. This translates to animal production when this growth is consumed by grazing livestock. Canopy LI was measured in six pasture systems within three physiographic regions in West Virginia, across two grazing seasons and a range of pasture regrowth to quantify how LI is impacted by pasture height (ruler height [RHt] and falling plate meter compressed height [CHt]), sward composition, and time of year. The relationship between CHt and LI was computed as second-order and logarithmic regressions. The second-order regressions gave slightly greater R-2 and lower residual standard deviations about the regression (SDreg) than did logarithmic regressions. Canopy LI reached 95% of incident light when CHt reached 8 inch (RHt of 13 inch) and was affected by forage density (FD; lb dry matter/acre/inch CHt, a system characteristic), forb and legume content in the stand, and month of the year. Understanding the effect of canopy height on LI and the effect of canopy height and LI on management goals will enable producers to adjust management to better achieve defined animal and plant performance goals.