The seed zone is warmer the closer the seeds are to the soil surface, acknowledges Hicks. So planting shallow when planting early might seem to promote more rapid germination and emergence.
Yet he still recommends the 2” planting depth regardless of planting date.
“I think there will be fewer potential problems later with a 2” depth. With normal weather, the soil is on a warming trend. The extra few days to emerge for corn planted 2” deep vs. 1-1 1/2” deep is not worth the risk of poor root development that can result from shallow planting.”
Another consideration is that the seedbed may settle, especially if it rains. “When this happens, the seed doesn’t move much from where it was placed in the soil,” says Hicks.
“However, the seed ends up at a shallower depth because the surface has settled. If the surface settles enough, the crown of the plant is very close to the surface. This may result in reduced and poor secondary root development. And the secondary roots are the permanent roots of the corn plant.”