Great Corn Harvest but Compaction Nipped Some Yields

Chad Lee, Extension Agronomist, University of Kentucky

The ear on the left is on a plant with
roots limited by compaction and the
other is on a plant with no compaction.

The corn yields being reported are excellent to date for Kentucky. With the wet weather at planting, we all were very concerned about compaction problems. The continued wet weather helped a lot of corn roots break through compaction. We dodged a disaster, but corn yields were dinged by the compaction. I walked a field yesterday where we think we may have lost as much as 75 bushels per acre to compaction.

That's the bad news. The good news is that the field went about 250 bushels per acre. That's an excellent yield in most fields and especially in a field with some compaction.

The roots overall in the field looked excellent and originally appeared to have no compaction. Then, we found the ear on the right in the picture. When we dug up that plant, the roots grew twice as deep as the roots of the plant on the left. The majority of the corn in this field looked like the ear on the left.

Corn in this field was at a high population (43,000 plants per acre). The ear on the right has about 160 more kernels. With the high population and that many extra kernels, we get the 75 extra bushels. There are two things to caution here: 1) When we simply compare these two ears, we are assuming that if compaction had not been an issue, then all ears would look like the one on the right; and 2) the field had some perennial weeds that needed to be removed with tillage this spring. That tillage led to the compaction. However, without controlling those perennial weeds, this corn would never have gotten close to the 250 bushel mark.

Stephanie Halcomb holding a plant with no compaction.
Yield potential was phenomenal this year.

So, these farmers did what they needed to do to remove the most limiting factor: in this case, used tillage to remove weeds. But that tillage this spring created some compaction. That compaction became the most limiting factor. Perhaps, this serves as a good reminder that tillage should only be done when absolutely necessary.