Cover crop and nitrogen rate management practices influence corn (Zea mays) NDVI and nitrogen content

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.). We evaluated corn NDVI
(normalized difference vegetation index) and leaf N (at six leaf, ear
leaf, 75% silk, and physiological maturity), over three growing seasons in
response to factorial treatments of cover crop (annual ryegrass [Lolium
perenne L. ssp. multiflorum (Lam.) Husnot], radish [Raphanus sativus L.],
and no-cover control) and N rate (0X, 0.25X, 0.5X, and 1X) relative to the
recommended rate based on pre-plant soil tests (157–190 kg N ha–1). 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 the
no-cover control, but annual ryegrass decreased NDVI relative to no-cover
control. This response to cover crop treatment suggests that radish cover
crop may improve corn nutritional status. Corn receiving 1X N rate had the
slowest decrease in leaf N over the growing season, 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 can be used with little effect on nutritional
status of corn following spring wheat in the northern Corn belt.