Cereals discrimination based on spectral measurements

The aim of this study is the discrimination of the main cereals cultivated in Greece (namely soft and durum wheat, barley and oat), using spectral data. In a field experiment, the spectral response in the visible and the near infrared was measured over the above crops, during a 17-week period from early growth to harvesting, for five days a week. An 8-channel ground-based hand-held radiometer, with spectral wavelength range 500-850 nm, was used for the measurements of the spectral reflectance. The ratio vegetation index (RVI) and the normalised difference vegetation index (NDVI) values were also calculated, using all combinations between the near infrared and the visible bands. The results show that all reflectance values are developed in similar way, as canopy geometry was almost similar for all four crops. However, oat presents remarkable differences with regards to the three other crops, in bands 7 and 8. NDVI and RVI values for oat also present the same differences with respect to the rest crops and these differences are better distinguished in some of the studied weeks. A statistical analysis based on the above observations confirmed the significance of the differences of the spectral values between crop pairs, for only the first eight weeks of the studied period. Moreover, differences between the three other crops (soft and durum wheat and barley) are very small. For discrimination applications, the more bands available, the better the chances for detection and identification.