 This paper examined the potential of Sentinel-1 synthetic aperture radar, SAR, to monitor crop conditions. It found that the cross-ratio, CR, which is calculated from the ratio of VH to VV backscatter, was the most effective indicator of vegetation dynamics. The CR was able to explain up to 87% of the variation in vegetation water content, VWC, for corn and winter cereal crops, and up to 63% for oil seed rape. Additionally, it was found that the CR could be used to accurately predict the timing of key phenological events such as flowering and maturity. This article was authored by Mariette Rugdenhill, Wolfgang Wagner, Bernhard Bauer Marschlinger, and others.