for LAI estimation over soybeans (low biomass crop) and corn (high biomass crop) canopies. A new LAI estimation approach is developed based on coupling of two existing models, the Water Cloud Model (WCM) and theUlabymodel . Previous research on SAR sensitivity to LAI has been primarily empirically based, with simple statistical models developed and inverted to estimate LAI . This study proposes a semiempirical approach,which when well calibrated is likely to be more robustwhen applied within its range of validity. The models developed in this study are applicable to a range of LAI from 0.04–4.79 for corn fields and from 0.07–3.57 for soybean fields.