AbstractSpectral reflectance measurements were found useful in estimating the dry green biomass (DGB) in hayfields in eastern Québec, Canada. The calibrated measurements of reflectance obtained in the 650 and 800 nm bands (respectively defined as the RED and NIR indices), the NIR/RED ratio, and the ratio (NIR‐RED)/(NIR + RED) were used to generate various regression models which explained between 74 and 90% of the variance in DGB. The proportion of legumes, grasses and herbs in the canopy had no apparent influence on the reflectance measurements or on the value of the mode