Predicting Native Warm-Season Grass Characteristics Using near-Infrared Reflectance Spectroscopy.

Native warm-season grasses are used in conservation reserve programs, grazing systems, and are currently investigated as bioenergy crops. Producers utilize warm-season grasses in complementary grazing systems to optimize forage production by grazing warm- and cool-season grass pastures during their respective prime production periods. Switchgrass (Panicum virgatum L.), a native warm-season grass, has been investigated as a bioenergy crop, due to its adaptation to a wide range of environmental conditions, soil types, and its high, stable yields. Calibration equations were developed using a modified partial least squares (MPLS) regression to investigate the relationship between laboratory analysis for acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), and carbon (C) concentration and NIRS spectra data of 4 native warm-season grasses: big bluestem (Andropogon gerardii Vitman), eastern gamagrass (Tripsacum dactyloides (L.) L.), indiangrass (Sorghastrum nutans (L.) Nash), and switchgrass. Material was obtained from the UK Variety Trials and switchgrass from the UK Switchgrass Biomass Project. One calibration examined all available material of the 4 grasses, while another used only switchgrass material. The calibration constructed using the 4 grasses was valid in predicting NDF, ADF, and CP, but not for C. The switchgrass calibration reported the biomass switchgrass material as outliers. Therefore, biomass switchgrass and forage quality switchgrass need to be analyzed using discrete calibration equations. The biomass switchgrass calibration was less accurate at predicting NDF and ADF, similar for CP, but much better for C compared to the 4 warm-season grass calibration. The forage switchgrass calibration was similar at predicting NDF and CP, but poor for C and ADF compared to the 4 warm-season grass calibration. In conclusion, the 4 warm-season grass calibration is valid in predicting native warm-season grass forage quality, and the biomass switchgrass calibration is valid in predicting C concentration of material harvested for biomass.