Remotely sensed estimation of rice nitrogen cencentration for forcing crop growth models

Precise phenological calendars, for each species and cultivar, are necessary both to highlight anomalous agronomic situations and to feed crop modeling. This study, conducted in the Italian Rice Area, focuses on the evaluation of the contribution of Remote Sensing data to provide phenological information of rice cropping systems. The temporal signal of three years (2002 to 2004) of MODIS NDVI 16-day composites was analyzed with TIMESAT program in order to automatically retrieve key phenological stages such as start of season (SOS), peak LAI (i.e. heading) and maturity. Procedure involved three steps: download of MODIS data, interpolation and smoothing of NDVI temporal profile and temporal signal analysis. Results of this procedure were evaluated acquiring information regarding cultivated variety, sowing dates, management and production from rice farmers. Good correlation (r2 = 0.97) has been observed between satellite-derived estimates and the phenological estimates produced with traditional Growing Degree Days (GDD) method based on thermal unit accumulation. The results show the usefulness of remote sensing data for the determination of phenological stages in order to initialize or performe runtime calibration of crop models in a spatially distributed way. Keywords