I've been getting a lot of calls about uneven corn. Uneven corn can be caused by many factors, and there are usually multiple variables in play. Since a lot of folks have asked, here are some reasons I am seeing uneven spots in fields around west central and southwest Iowa:
1. Cold, wet soils early in the season that limited early root formation, followed by dry (and hard) soils that aren’t as conducive to root growth.
2. Heavy residue areas. In some areas there seems to be more residue than normal this year, which lowers soil temps and can keep soils cooler.
3. Compacted areas--both sidewall and right under the seminal root system, about 3-4 inches below. Some agronomists theorize that the lack of a good freeze/thaw cycle contributed to this. We are even finding it in long-term, no-till fields, which likely means this isn’t something we did, but more a mother-nature issue.
4. NH3 burn.
5. Insect injury to crown and/or mesocotyl.
6. Early season seedling disease of mesocotyl and/or crown.
7. A few cases of herbicide injury/carryover.
8. Soil temperatures variations--usually a result of lighter colored soils, wet areas, and/or heavier residue cover.
9. Tillage patterns--especially anything done mid-spring after we started getting some moisture.
10. Extra soil washed in where trash whippers “trenched” a furrow in the row resulting in very deep planted corn (3 inches or more).
11. Loose, dry, and “fluffy” soil (not my term, by the way) in the seed zone that settled with some of the early rains. This shallowed up some guys planting depth by .5-1 inch or more… setting us up for trying to throw nodal roots shallower than we’d like to see.
12. Some areas where heavy rains washed soil out of the row, resulting in very shallow (1 inch or less) planted corn and the corresponding dreaded “rootless corn syndrome.” This was especially bad in tilled fields and fields where trash whippers were run deeper into the soil.
13. Sidewall smearing/compaction. I’ve seen quite a bit of this with some of our middle and later planting windows this year.
Related articles:
Uneven corn management and prevention
Clarke McGrath On-Farm Research and Extension Coordinator - Iowa Soybean Research Center
Clarke McGrath currently serves as the On-Farm Research and Extension Coordinator.
Prior to joining Iowa State University, McGrath spent nearly a decade as a retail agronomist and manager in the GROWMARK system, earni...