I have not seen much corn planted yet here in Wayne County at the end of April, but that will change soon. Growers should make sure that planters are adjusted to put corn in at a proper depth. Corn is a large seed with a lot of vigor and capable of germinating and emerging from several inches deep without too many problems. Personally, I have seen corn emerge from a 6+ inch planting depth (planter adjustment error). While that is obviously an extreme and not recommended condition, generally it may be better to err on the side of deeper planting rather than too shallow. Recently OSU Extension corn specialist Peter Thomison wrote about corn planting depth in the OSU Extension CORN newsletter. Here is an excerpt from that article summarizing some important points. The entire article is available on-line at: https://agcrops.osu.edu/ .
Planting depth recommendations for Ohio are 1.5 to 2 inches deep to ensure adequate moisture uptake and seed-soil contact. Deeper planting may be recommended as the season progresses and soils become warmer and drier, however planting shallower than 1.5 inches is generally not recommended at any planting date or in any soil type. When corn is planted 1.5 to 2 inches deep, the nodal roots will develop about 0.75 inches below the soil surface. However, at planting depths less than 1 inch, the nodal roots develop at or just below the soil surface. Excessively shallow planting can cause slow, uneven emergence due to soil moisture variation, and rootless corn (“floppy corn syndrome”) later in the season when hot, dry weather inhibits nodal root development (Nielsen, 2010). According to some field agronomists, shallow plantings increase stress and result in less developed roots, smaller stalk diameters, smaller ears and reduced yields. In a recent OSU evaluation of planting depths, grain yields were about 14% greater for the 1.5-inch and 3-inch planting depths than the 0.5-inch planting depth in 2011, and 40% greater in 2012. The lower yields of the shallow planting were associated with a reduced final stands and 6 to 7 times as many “runt” plants as the other two planting depths.
In a 2013-2014 Cornell University study comparing planting depth across a range of soil types and plant populations, Cox and Cherney (2015) concluded that optimum seeding depth differed across sites and at times across years within sites. Additionally, the risks of reduced population or grain yield were generally greater at the shallow seeding depth compared with the deeper depth (2.5 inches). Research at Kansas State University (Roozeboom, 2012) that evaluated six planting depths ranging from 1 to 3.5 in. supported planting depth recommendations of 1.5 to 2.5 inches depending on soil conditions