The response of a sorghum sudangrass cover crop to residual nitrogen and its relationship with spectral sensors

A sorghum sudangrass (SSG) cover crop grown after a cash crop could take up residual nitrogen (N) before it is lost. As in‐field monitoring of SSG properties is laborious, predicting biomass and N concentrations with spectral sensors could be useful. At two sites in Live Oak, Florida, we evaluated the response of SSG to residual N from previous N fertilization and the performance of handheld and satellite sensors in estimating SSG properties. We quantified aboveground biomass, plant N, leaf greenness (NDVI), net potential N mineralization (PNM), and soil permanganate oxidizable carbon (POXC). Residual N did not affect SSG properties, PNM was highest at the highest N input rate in one site, and soil POXC was correlated with SSG properties (biomass and plant N). NDVI measured from a handheld sensor better predicted SSG properties than satellite imagery in these small plots, suggesting a greater potential to be a useful management tool. Core Ideas Sorghum sudangrass growth was not influenced by residual nitrogen (N) from a previous corn crop. In one of two fields, potential N mineralization was highest with the highest N input rate applied to corn. Normalized difference vegetation index derived from a handheld sensor was more predictive of cover crop properties than satellite imagery.