How Much Nitrogen Does Your Corn Need?

Sally Krueger

17 June 2018

Corn plants use large quantities of nitrogen (N) to grow and yield. Corn removes 1 pound of nitrogen for every bushel of grain produced, so a 250 bushel per acre yield goal requires 250 pounds of nitrogen available to be used by your growing corn plants.

Each Growth Stage Requires Different Nitrogen Amounts

Corn will accumulate 65% of the total nitrogen need by the time flowering begins. In the seedling stage of corn growth through V5 (5 leaf), corn plants have taken in approximately 10% of total nitrogen needed. It may be the most important 10% used because ear size, as well as both rows around and row length, are developing then. A shortage of nitrogen at V5 can cause reduced ear size formation and lessen yield potential, which cannot be reversed as the plant continues to grow.

During the rapid growth stage, or V6 (6 leaf) to V18 (18 leaf), corn will absorb up to 8 pounds of nitrogen per acre per day. If environmental conditions are right, corn plants can grow more than 4 inches per day. A nitrogen shortage at this stage of corn development can result in a significant and permanent yield loss. Look for yellowing corn leaves and any aborted kernels on the ear tips as symptoms of a nitrogen deficiency.

How Much Nitrogen Is Too Much Nitrogen?

Nitrogen is one of the most expensive nutrients applied in corn production. That is typically due to the quantity of N that corn requires. It makes sense not to over-apply from an efficiency standpoint, but over-applying nitrogen can have a negative effect on yield, too.

Stalk rot diseases flourish in high nitrogen environments and can cause premature plant death and stalk lodging, which makes machine harvest difficult and can cause some grain loss.

Get Nitrogen Credits Where You Can

Once a reasonable yield goal has been established for your crop, credits for residual nitrogen from a soil and water analysis (if you’re growing irrigated corn) can be deducted from the total amount of nitrogen your crop needs. If a legume crop was grown in rotation, you should deduct a reasonable credit for estimated nitrogen produced naturally by those plants. Also, be sure to deduct any nitrogen applied as a starter fertilizer and any nitrogen used as a herbicide carrier.

Applying Just Enough Nitrogen

Split applications of nitrogen prevents nitrogen losses from leaching and other volatilization issues, and they are more efficient than applying the total amount of nitrogen required as preplant. This time of year, sidedressing nitrogen will soon be completed. However, if you’re injecting nitrogen through a pivot, now is the time to apply so you can reduce your chances of not being able to do so later due to rain.

All in all, it is best to have all of your nitrogen applied to corn before R1 (or silk emergence) because nitrogen applied after that stage is not as efficient and generally has little, if any, impact on your final yield.

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Sally Krueger

17 June 2018