PREDICTION OF LEAF/STEM RATIO USING NEAR-INFRARED REFLECTANCE SPECTROSCOPY (NIRS): A TECHNICAL NOTE

Leaf/stem ratio of grass stands is an important factor affecting diet selection, quality, and forage intake. Determination of leaf/stem ratio involves a labor-intensive process of hand separating leaf and stem fractions. Our objectives in this study were to evaluate leaf/stem ratio prediction using near-infrared reflectance spectroscopy (NIRS) in monocultures of big bluestem (Andropogon gerardii Vitman), switch- grass (Panicum virgatum L.), intermediate wheatgrass [Thinopyrum intermedian (Host) Barkw. & D.R. Dewey], and smooth bromegrass (Bromus inermis Leyss.). Samples of each species were hand-clipped from monocultures at four locations throughout Nebraska in the 1997 and 1998 growing seasons. Ground samples were scanned by a Per- storp model 6500 near-infrared scanning monochromator. Calibration equations were developed using CENTER and SELECT procedures. Near-infrared reflectance spectroscopy estimated leaf/stem ratio in monocultures of big bluestem, switchgrass, intermediate wheatgrass, and smooth bromegrass with a coefficient of determination (r2) 0.73, 0.96, 0.75, and 0.84, respectively. Near-infrared reflectance spectroscopy was a rapid means of estimating leaf/stem ratio in these grasses