A low cost portable spectroradiometer able to operate in the 4 bands of the satellite system Landsat MSS was developed. The radiometer was designed to measure the spectral reflectance of spatially extended targets. Spectral bands were selected with 10 nm bandwidth filters. Measurements were made during 2003, from seedtime to harvest, on an experimental plot of wheat. The culture was divided in parcels that received different treatments (seed variety, fertilizer, herbicide and fungicide). Weekly measurements with the detector at nadir and the sun near midday were made. As result of the spectral measurements of reflectance, the normalized difference vegetation index (NDVI) was calculated. As a comparison, LAI, chlorophyll concentration and diverse gravimetric determinations, were carried out. The results were analyzed by means of statistical techniques and showed a good correlation between the optical index and the culture variables. In the future the geometry of the measurement will be improved to reduce the effect of the canopy and other channel in the near infrared will be added to distinguish water and nitrogen stress.
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