Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2022
Publication Date: 6/8/2022
Citation: Scott, D.A., Johnson, J.M., Gesch, R.W. 2022. Cover crop and nitrogen rate management practices influence corn NDVI and nitrogen content. Agronomy Journal. 114:2473-2483. https://doi.org/10.1002/agj2.21085.
DOI: https://doi.org/10.1002/agj2.21085

Interpretive Summary: Winter cover crops are rarely used in the northern corn belt because of short growing seasons. Planting a winter cover crop after wheat and prior to corn allows more time for the cover crop to establish and influence the next cash crop (corn). The findings of this work are relevant to farmers growing corn after wheat in the northern Corn Belt. This work suggests that corn grown after radish is greener throughout the growing season compared to corn grown after annual rye or no cover. However, cover crop had no impact on grain N content. This work also suggests that half the recommended rate of N fertilizer results in corn with similar nitrogen content and similar yields as the full recommended rate. Halved fertilizer use could lower operating costs.

Technical Abstract: Cover crops are rarely adopted in the northern Corn Belt because of short growing periods but could provide benefits when grown between wheat (Triticum aestivum L.) and corn (Zea mays L.). Use of synthetic fertilizer has allowed very productive corn systems but has potential to cause environmental harm. We evaluated corn health, as indicated by NDVI and leaf N, over three growing seasons in response to factorial treatments of cover crop (annual rye [Lolium perenne L. ssp. multiflorum (Lam.) Husnot], radish [Raphanus sativus L.], and no-cover control) and N rate relative to the recommended rate (0X, 0.25X, 0.5X, and 1X). Grain N was also measured in the last study year (2016) to evaluate if leaf N indicated grain N. Radish cover crop increased corn NDVI relative to that in the no cover-control, but annual rye decreased NDVI relative to no-cover control. This response to cover crop treatment suggests that radish cover crop can improve pre-reproductive health of corn. Corn receiving the full (1X) N rate had the slowest decrease in leaf N, but 2016 data revealed that grain from all treatments receiving some level of N had similar N content. Root biomass was also highest in the 0.5X N rate treatment and could explain the previously reported result that 0.5X N rate results in highest corn yield. Taken together, these results suggest that half the recommended N fertilizer rate can be used with little impact on corn health.