DETERMINATION OF FORAGE CHEMICAL COMPOSITION USING REMOTE SENSING

Authors: Starks, Patrick; Coleman, Samuel; Phillips, William

Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2004
Publication Date: 11/1/2004
Citation: Starks, P.J., Coleman, S.W., Phillips, W.A. 2004. Determination of forage chemical composition using remote sensing. Journal of Range Management. 57(6):635-640.

Interpretive Summary: Traditional forage nutrient analysis from bench-top near infrared spectroscopy (NIRS) or common laboratory chemical procedures provide accurate, point-based information, but often do not provide it in a timely way to allow changes in forage or livestock management. Further, these approaches do not lend themselves to assessments of forage quality prior to grazing or harvesting. The objectives of this study were to determine the feasibility of estimating concentrations of nitrogen (N), neutral detergent fiber (NDF) and acid detergent fiber (ADF) of live, standing forages using a hand-held hyperspectral spectroradiometer, and to compare these estimates to values determined via NIRS and laboratory chemical methods. Calibration equations were developed from canopy reflectance measurements of bermudagrass and then applied to a test data set to predict N, NDF and ADF. Statistical analyses showed that estimates of N, NDF, and ADF from the radiometer were equivalent to those from the NIRS. Such a remote sensing approach would enable real-time assessment of forage quality, would allow mapping of the nutritional landscape, could be used as a tool to better manage pastures and supplements, and would assist in making harvesting decisions.

Technical Abstract: Traditional forage nutrient analysis from bench-top near infrared spectroscopy (NIRS) or common laboratory chemical procedures provide accurate, point-based information, but often do not provide it in a timely way to allow changes in forage or animal management. Further, these approaches do not lend themselves to assessments of forage quality prior to grazing or harvesting. The objective of this study was to determine the feasibility of estimating concentrations of nitrogen (N), neutral detergent fiber (NDF) and acid detergent fiber (ADF) of live, standing forages using a hand-held hyperspectral spectroradiometer (radiometer). These estimates were compared to values determined from benchtop NIRS and laboratory chemical methods. Calibration equations were developed from canopy reflectance measurements of bermudagrass and then applied to a test data set to predict N, NDF and ADF. Statistical analyses showed that estimates of N, NDF, and ADF from the radiometer explained from 63 to 76 percent of the variability expressed in the laboratory data, and were equivalent to those estimates derived from the NIRS. Such a remote sensing approach would enable real-time assessment of forage quality, would allow mapping of the nutritional landscape, could be used as a tool to better manage pastures and supplements, and would assist in making harvesting decisions.