 This study uses Sentinel-1 and Sentinel-2 archives to map fallow fields in a farming pastoral ecotone in northern China, with a 10M resolution fallow map generated for 2020. The study also evaluates the time series characteristics of the entropy eigenvalues generated via dual polarization decomposition and tests the mapping method at different time intervals to optimize fallow field monitoring. The results demonstrate the potential applicability of Sentinel archives for monitoring and mapping agricultural land management patterns in a region. This article was authored by Deji Wu, Liang Sun, Cheng Sun, and others.