From the Field

March 10, 2010 06:00 PM
Q I'm a dairy farmer who uses cattle manure as the nitrogen source for my corn crop. For corn on corn, I knife the manure in the field in the fall and then chisel the cornstalks. In the spring, I make a pass to level the field and then plant. Shortly after the corn comes up, it looks yellow and sickly. Is the nitrogen in my manure any good, and should I really count it in my program?
—Southern Wisconsin

A The nitrogen in your manure is as good as any other source of nitrogen you can buy. The sickly yellow corn you're seeing in the field is due to the timing and placement of your nitrogen application.
Neither manure nor banded nitrogen do a good job of paying the carbon penalty in the spring because the manure has to decompose to become available to the corn. You're applying the nitrogen in a concentrated form, which doesn't help the breakdown of residue on the surface, and it's too far away from the small plant.

Once your corn plant gets enough depth of root, it should reach the nitrogen and pick up its color to turn green. But corn can go through a tough period before its roots reach the source of nitrogen. Think about backing up your manure rate. And save some of your nitrogen to apply in a spring surface application or put some of the nitrogen allotment on with your corn planter. Applying nitrogen with the planter will help the corn early on until it can grow to reach the banded manure.

For the past two years, the farmers in our neighborhood who have been sidedressing have been coming out with a lot higher yields. With the tight window to get sidedressing done, I'm worried about finding the time to sneak between the rows. By adding a nitrogen inhibitor in my spring nitrogen application, can I eliminate the need for sidedressing?
—Central Indiana

A It's possible to use a nitrogen inhibitor to achieve your goal. But remember, our objective is to never let corn have a bad day.

One of the main reasons your neighbors who sidedress have seen such a strong yield response is the environmental conditions we've had for the past couple of years. The large amount of rainfall we've received throughout the growing season has led to increased leaching. As a result, splitting nitrogen applications helps protect against nitrogen loss. Using a nitrification inhibitor can help slow down the release of nitrogen, which increases its longevity, especially in soils that are susceptible to leaching and denitrification.
Remember that nitrate is what the corn plant wants. While you are trying to inhibit nitrate formation, make sure you don't create a nitrate shortage. For instance, if we were rescuing corn that was nitrogen-deficient, we wouldn't want to use an inhibitor to slow it down because the corn needs the nitrogen. Same way with corn on corn in the spring: If we put a nitrogen inhibitor on with our spring application, it may work too well and stop nitrogen from converting to nitrate. This would create temporary nitrogen shortages for the plant as it's dealing with carbon penalty.

The trick is to not inhibit all of the nitrogen or to put some nitrogen down with the planter to keep the corn plant green early.

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