Nitrogen rate: Was it right?

Farm Forum

Checking corn fields now when still green can tell how well the corn was fertilized with nitrogen. In most fields right now there are bottom leaves that are yellowing from the tip down the midrib towards the stalk. In time this area will brown as the stress increases. It also will move up the plant to higher leaves. These symptoms should not be confused will yellow plants that maybe in low areas that were too wet early in the season and did not fully develop. This year with the late dry conditions there is more extensive leaf firing and it is occurring on leaves higher on the plant. This could be due to two factors. One could be that the rate was not high enough for the amount of corn the field is trying to produce. Secondly with the dry conditions in the top of the profile the corn may have not been able to use all of the available nitrogen in the soil because of the dry soil in the top of the profile.

One way to check this is to do an estimated yield check on some ears in the corn field. If your yield goal was 150 bushels and your yield check indicates 190 bushel corn this may be part of the cause.

Work from Iowa State University that was confirmed by research from Penn State University indicates that if the firing has not reached the leaf below the primary ear leaf, there is a 90 percent chance that yield was not reduced.

To make sure you have enough nitrogen after harvest soil test the field with a 2 foot soil test. If you have between 50-70 lbs left in carryover the field was fertilized about right if the less you may have lost some yield. If more, you will have carryover for next year.