RapidEye's five satellites to be launched in the summer of 2008 will make it possible to regularly monitor the N-status of crops from space. The sensors on board of each satellite are equipped with five broad bands: blue, green, red, rededge, and NIR. This opens new avenues for red-edge based algorithms to predict the N-status of cereals. In a study conducted in Montana in 2007, we obtained the best results to predict tissue N content (TNC) of irrigated spring wheat and barley, as well as dryland barley from the following algorithm, based on light reflectance (R) of the canopy in the red, red-edge, and NIR bands: ( TNC= RNIR - Rred-edge )/( RNIR -s* Rred ) where s stands for slope of the soil line, i.e. the separately measured bare soil reflectance of the NIR band divided by the red band. Red-edge band based algorithms will open new avenues to optimize in-season N management of cereals, and for monitoring and verifying the efficacy of N fertilization.
