One of my biggest pet peeves when it comes to crop production is shallow planting. Adoption of no-till and strip till farming practices is on the increase. The biggest issue that comes with those practices is uneven planting depths. The importance of correct planting depth is sometimes over shadowed by the spacing. But, in my eyes, if the depth is not correct then spacing means nothing. Iowa State University says that optimum planting depths for corn should be 1.75 to 2.25 inches, with the optimum being 2.0 inches. I prefer 2.25 inches as the depth to shoot for. One should not see more then about a .25 inch variance either way when checking the planter across a field.
The one thing that I see almost every year is a grower that starts planting late and the soil conditions are dry so he will plant shallow, hoping to catch a rain so everything germinates. This is in every instance the worst possible thing a grower can do. The soil surface, especially in the top 2 inches, is the first thing to dry out. Shallow planting in dry soils can cause issues with seminal and nodal root development. In dry conditions roots near the soil surface are often aborted. Roots take up nutrients. Nutrients can only pass through the plant in a water solution. Root development needs to start where there is the least chance of the soil drying out. In most cases that is at a depth greater than 2 inches.
A second reason to plant at a depth of 2.0 inches and deeper has to do with soil temperature and crop emergence. The temperature varies greatly in the top 2 inches of the soil profile especially in no-till and strip-tilled fields. Soil type and crop residue in close proximity to the row have tremendous effects on soil temperatures as well. Again, soil moisture tends to vary in the top 2 inches of the soil profile, thus the soil temperature varies also. In order to get even crop germination and emergence you want to plant at a depth with fewer variables.
Another reason to stay at a depth of 2.0 inches and deeper is that most pre-emerge herbicides leach through the soil to a depth of .5 to 1.5 inches. By staying below this you decrease your chances of herbicide injury to early seedlings.
Other issues that are often associated with shallow planting are poor stalk development, poor brace root development, and above all reduced yield.
To this day I have still not been in a field where planting too deep caused any issues. I have been in fields where shallow planting was the beginning cause of many issues within a field. Be sure to get your planting depth correct.