Monitoring Corn Crop Height and Growth Rate With Interferometric Coherence

Future radar Earth observation missions, with reduced revisit times, will offer the capability to obtain valuable data applicable to agriculture and meteorology. They will contribute to a better understanding of some observed changes that exhibit time scales much shorter than present satellite revisit times. In the context of the preparatory studies in support of future radar mission proposals with reduced revisit time, such as the geosynchronous HydroTerra, the HydroSoil facility has been set up for C-band radar continuous monitoring of crops with a time resolution of 10 min and a spatial resolution of 1 m ² . The data obtained for a corn crop observed along the life cycle has been analyzed to model radar backscattering dependence on crop development parameters. In this study, it is particularly noticeable that the interferometric coherence was measured over a 24-h interval, in contrast to previous studies. Coherence has shown a strong sensitivity to plant height and the phenological stage of the crop, which can be exploited to sense crop growth with radar measurements. However, due to the high density and size of the developed corn canopy, the relationship between coherence and crop height is limited to the first corn stages. For this reason, a new parameter named daily growth rate has been defined and found to be well correlated with the radar coherence.