In this investigation, we examine the relationship between polarimetric radar data, VWC, and several vegetation indices. The major focus is on the use of the proposed radar vegetation index (RVI) [12]. The data utilized were obtained with a ground-based multifrequency polarimetric radar system that provided measurements every 10 min over the crop growing season. Two different crop types (rice and soybean) were investigated. These observations were analyzed to determine what new information can be extracted from current and future radar satellite systems on the vegetation condition, specifically the VWC, of two globally important crop types. It should be noted that the radar system used operated at a single incidence angle of 40◦, and therefore, the results are directly applicable to systems such as the proposed National Aeronautics and Space Administration Soil Moisture Active Passive (SMAP) satellite.