Estimating Nitrogen Content in Winter Cover Crops Using Sentinel-2 Red-Edge Indices

Maryland incentivizes winter cover crops to reduce agricultural erosion and nutrient runoff into the Chesapeake Bay. While cereal cover crops can reduce nitrate leaching 50-95%, performance varies and is challenging to monitor at scale with more than 25,000 fields planted each year in Maryland. Satellite remote sensing using red-edge bands (705 nm, 740 nm, 783 nm) has been shown to effectively estimate N content (N pool within aboveground biomass) in later growth stage crops. We evaluated fourteen red-edge indices derived from Sentinel 2 imagery using 908 cereal cover crop destructive samples collected from 2019-2021 at the Beltsville Agricultural Research Center and the Eastern Shore of Maryland. Delta Red-Edge was the best predictor of N content (R2=0.752) using a subset of the samples with imagery collected within +/- 4 days of destructive sample (n=601). Cross-validation of models was performed using samples collected from 2021-2022 (n =450).