Question: What could cause an uneven stand of corn?

Answer:
There can be multiple issues that can cause uneven corn stands:
 
Some possibilities for you to rule out:
1.) Herbicide injury

2.) Disease

3.) Uneven stands because of replanting

4.) Issues with soil to seed contact due to severe surface crusting/compaction

5.) Issues due to low soil temperatures (less than 50 degrees)

6.) Uneven soil moisture

7.) Corn nematodes - The U of I Plant Clinic can evaluate soil samples for corn nematodes. If you suspect or would like to rule out corn nematodes as a problem, you are more than welcome to submit a composite soil sample to the U of I Plant Clinic for evaluation. For additional information on symptoms or sampling, you can refer to the following links:
http://web.extension.illinois.edu/state/newsdetail.cfm?NewsID=27515
http://web.extension.illinois.edu/plantclinic/downloads/1100-revised.pdf

Most problems this year were attributed to poor soil conditions at planting; however, we need to rule out all of the possibilities listed above. Further information on uneven corn stands can be found at the following links:
http://www.agry.purdue.edu/ext/corn/news/timeless/germemergreq.html
http://www.extension.purdue.edu/extmedia/NCH/NCH-36.html