Cover Crops Suck Up Nitrogen As Expected

Amazing photos of cover crops grabbing nitrogen prove the point.

Published on: Oct 22, 2012

Agronomists' advice for those with poor corn crops coming out of the drought this fall was to plant cover crops to capture the nitrogen. The theory was that if cover crops could get established in time, they could catch nitrogen before it leaches down below the tile zone. Otherwise the nitrogen is likely to be lost to leaching during the winter and spring, especially if there are periods or warm, wet weather when soils are saturated.

Lisa Holscher, a watershed coordinator in west-central Indiana, based in Sullivan, provides proof that this theory was on target. She has circulated pictures from Mike Bell, Sullivan, who established a cover crop relatively early in a corn field where performance was well below par.

Green Strip: Here is living proof that cover crops find nitrogen left behind and not used by a corn crop. Notice the dark green strips.
Green Strip: Here is living proof that cover crops find nitrogen left behind and not used by a corn crop. Notice the dark green strips.

Just from the photo, it's obvious that the cover crop growing over where the nitrogen was applied last spring and summer is much greener and taller. Obviously the roots of the cover crop have tapped into the nitrogen than the corn roots couldn't get to because the soil was too dry for uptake. As many expected, a large share of the nitrogen remains in bands close to where it was applied.

This visual proof indicates that the cover crop is capturing nitrogen. It will release it slowly once the cover crop is killed next spring. But the nitrogen won't be lost into the environment through leaching into tile lines and running of into waterways.

If you didn't plant a cover crop and your corn yield was poor, loss into waterways once the soil becomes saturated before planting time next spring is likely. The window for planting cover crops is closing, but most experts say there is still time to plant a wheat or rye cover crop. However, whether it gets big enough this fall to capture a sufficient amount of nitrogen will depend upon growing conditions after it is planted and emerges.