Special measurements of barley and clover canopy directional reflectance in the red and NIR spectral regions during vegetative growth were carried out to test the Nilson - Kuusk canopy reflectance model. The model reproduces adequately the measured angular distribution of red reflectance. Systematic differences are observed in the NIR spectral region. Using a simple inversion procedure, the canopy optical and structural parameters are determined from optical reflectance measurements in one or two spectral regions. The results of inversion agree reasonably well with those of phytometric measurements. The disagreement between the measured and calculated NIR reflectance profiles gives rise to difficulties in inversion in NIR channel, and this is the reason why simultaneous measurements in two spectral regions had no advantage in model parameter estimation. Obviously, the Nilson - Kuusk model needs some improvement in the NIR spectral region.
