Tracking crop phenological development of spring wheat using synthetic aperture radar (SAR) in northern Ontario, Canada

Information on crop phenological state such as flowering, maturing, drying, senescence, and harvesting is essential for crop production surveillance and yield prediction. Earth Observation data provide an important information source for monitoring crop development at various spatial scales. Crop phenological changes have long been related to optical spectral signatures such as the normalized difference vegetation index (NDVI) and spectral shifts in red-edge. In recent years, more efforts have been made to explore the sensitivity of synthetic aperture radar (SAR) to crop biophysical parameters. As an experiment, this study investigates the signal response (polarization and decomposition) of C-band SAR to spring wheat development in northern Ontario, Canada. Significant relationships were found between the SAR intensity (HH, HV) and crop height. R² values of 0.83 and 0.87 were achieved between crop height and the HH and HV polarization modes, respectively. An even higher correlation was found between the SAR decomposition parameter (Alpha angle) and crop height with an R² of 0.93. The close relationship between crop height and SAR response offers a viable means for using SAR to track crop growth.