During the dust bowl era, winter wheat growers were encouraged to purchase deep-furrow drills which would place seed somewhat closer to subsoil moisture. The surface (4-6") soil was too arid for seeds to germinate. These drills were the last resort for many farmers. However, wheat seedlings often perished with a few weeks, leaving the soil bare and subject to wind erosion. Why did the seedlings germinate and then fail so suddenly?
The temporary root system arising from the seed (primary and seminal roots) do not persist very long after seedling emergence. The permanent root system develops at a more shallow depth in the soil profile, arising from nodes at the base of the emerged shoots. This zone is called the crown.
The first evidence of the permanent root system (crown roots) is found when adventititous roots develop at the base of the coleoptile. This root system anchors the seedling and is essential for winter survival. However, in this instance, these roots perished due to lack of soil moisture in the surface 4-6 inches.
Wheat growers were lead to believe that deep planting would favor the establishment of a permanent root system at a somewhat greater depth in the soil. This was in error due to the well established fact that these roots arise from the node at the base of the coleoptile. This node lies within about one inch of the soil surface so deep planting was to no avail.