Drought is a major natural hazard that impacts agriculture, the environment, and socio-economic conditions. In 2018 and 2019, Europe experienced a severe drought due to below average precipitation and high temperatures. Drought stress affects the moisture content and structure of agricultural crops and can result in lower yields. Synthetic Aperture Radar (SAR) observations are sensitive to the dielectric and geometric characteristics of crops and underlying soils. This study uses data from ESA’s Sentinel-1 SAR satellite to investigate the influence of drought stress on major arable crops of the Netherlands, its regional variability and the impact of water management decisions on crop development. Sentinel-1 VV, VH and VH/VV backscatter data are used to quantify the variability in the spatio-temporal dynamics of agricultural crop parcels in response to drought. Results show that VV and VH backscatter values are 1 to 2 dB lower for crop parcels during the 2018 drought compared to values in 2017. In addition, the growth season indicated by the cross-ratio (CR, VH/VV) for maize and onion is shorter during the drought year. Differences due to irrigation restrictions are observed in backscatter response from maize parcels. Lower CR values in 2019 indicate the impact of drought on the start of the growing season. Results demonstrate that Sentinel-1 can detect changes in the seasonal cycle of arable crops in response to agricultural drought.@en

The systematic high temporal coverage of Sentinel-1 Synthetic Aperture Radar (SAR) is ideal for agricultural monitoring. The availability of these data on cloud computing infrastructure eliminates the need for massive computing power to process imagery. However, their distribution as SAR imagery still limits their accessibility for non-expert users. In Agricultural SandboxNL, Copernicus Sentinel-1 imagery on the Google Earth Engine (GEE) was mined to produce a database of spatially-tagged, parcel-level backscatter for every agricultural parcel in the Netherlands from 2017 to 2019. The database includes descriptors from the publicly available Basisregistratie Gewaspercelen, allowing the user to query the database by crop type and administrative boundary for any region of interest within The Netherlands. Publication of this database reduces the burden of processing and extracting a large volume of Sentinel-1 SAR data for experts. More importantly, it provides easy access to the Sentinel-1 data for agriculture/agronomy experts with limited SAR processing experience. In addition, the GEE package Sen1byParcel developed for Agricultural SandboxNL is made publicly available so that Sentinel-1 imagery can be extracted for any user-provided shapefile.@en