**8.3. Development of methodology for forecasting spatial crop age/phenology**

Response to abiotic stresses and quality of advice to farmers depends on the crop type and crop growth stages. The crop age or phenological stages depend on spectral emergence date/ sowing date and subsequent ambient temperature and sunshine hours expressed through thermal and helio-thermal units. The length of the growing season is determined from spectral emergence date and the date of physiological maturity.

Temporal profiles of vegetation index from satellite remote-sensing observations are modelled to trace back spectral emergence date. Early detection could be possible if high temporal vegetation index with a resolution varying from 200 to 1000 m depends on the crop type and coverage. The potential crop mask is an essential input to this. This work is being attempted for six major crops for which the potential crop masks are expected to be available. Superimposition of extended-range or medium-range weather forecasts with spectral emergence dates would provide crop age if agro-climatic zone-wise thermal thresholds are known.
