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Development of Canopy Reflectance Algorithms for Real-Time Prediction of Bermudagrass Pasture Biomass and Nutritive Values

^a USDA-ARS, Grazinglands Research Lab., El Reno, OK 73036
^b USDA-ARS, Subtropical Agricultural Research Station, Brooksville, FL 34601

View larger version (35K): [in a new window]   Fig. 1. Coefficients of determination (r2) of forage neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) concentrations (%), aboveground biomass (Mg ha–1), and CP availability (CPA, kg ha–1) with canopy reflectances in broad-wavebands of blue (450–520 nm), green (520–600 nm), red (630–690 nm), near infrared (NIR, 760–900 nm), short-wave infrared 1 (SWIR1, 1550–1750 nm), and short-wave infrared 2 (SWIR2, 2080–2350 nm) (n = 144).

View larger version (37K): [in a new window]   Fig. 2. Coefficients of determination (r2) vs. wavelengths for the relationships of forage neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) concentrations (%), aboveground biomass (Mg ha–1), and CP availability (CPA, kg ha–1) with (a) canopy reflectance, (b) reflectance ratios, and (c) the first derivatives of reflectance at different wavelengths. The r2 values were based on a linear model of the calibration data set. Typical wavebands where the reflectances, reflectance ratios or the first derivatives of reflectance have the greatest r2 (in parenthesis) with the forage quality parameters are highlighted in the figure (n = 72).

View larger version (50K): [in a new window]   Fig. 3. Comparison of laboratory measured forage neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP) concentrations, aboveground biomass, and CP availability (CPA) in the test data set with their predicted values based on the equations developed with (a) reflectance ratios, (b) first derivatives of reflectance, (c) stepwise regression of reflectance, and (d) stepwise regression of the first derivative of reflectance in Tables 2 and 3 (n = 72). Dotted line represents predicted = measured values.