RS spatial maps were obtained from RapidEyeTM satellite images. This platform collects data in five bands of the electromagnetic spectrum: Blue (440–510 nm), Green (520–590 nm), Red (630–685 nm), Red-Edge (690–730 nm) and Near Infrared (760–850 nm) at a spatial resolution of 5 m. Satellite acquisition dates were planned to correspond with the days before and after the second N fertilization. RS data were collected on 10 March 2009, 21 April 2009, 14 March 2010, and 7 April 2010. These dates correspond to 6 and 3 days before and 36 and 21 days after the second N application for the growing season 2008/2009 and 2009/10, respectively. Reflectance measurements acquired with a FieldSpec HandHeld ProTM portable spectroradiometer (Analytical Spectral Devices 2002) on the same dates of satellite images acquisitions were used for calibration of the satellite images. The instrument’s spectral range is between 325 and 1075 nm with a 10 nm bandwidth with a field of view of 25 . Readings were taken under clear sky conditions and converted to reflectance by referencing a 99 % Spectralon white panel (Labsphere 1998). All satellite images were georeferenced and coregistered in UTM WGS84 reference system and atmospherically corrected.