"While it is true that a field of young corn technically does not use a lot of water on a per acre basis every day, it nevertheless requires adequate soil moisture to support the initial development of the young plants' nodal root systems in the early leaf stages of stand establishment," Nielsen says. "The success or failure of the initial development of a corn plant’s nodal root system greatly influences the success or failure of the young corn plant in transitioning from 'life support' using kernel reserves to relying on the developing nodal root system for 'life support.'"
The V3 developmental stage -- when the plants have 3 leaf collars showing -- is a big one when it comes to root development. That's when the seed starts to shift from in-kernel energy to the nodal roots for nutrients to fuel growth. If something's limited those roots' development potential, it can take what looks like a healthy, uniform crop and sink it fast, Nielsen says.
"Corn younger than V3, still relying on its kernel reserves, can look pretty darn good and uniform. However, if severe stresses limit the development of the first few nodal sets of permanent roots, then the plants will struggle or fail to complete the transition from reliance on kernel reserves to reliance on nodal roots," he says. "Examples of severe stress that can limit this initial root development include seedling disease, repeated defoliation events, shallow soil compaction, corn rootworm injury, corn nematode injury, excessively wet surface soils, excessively dry surface soils, excessively cold surface soils, and excessively hot surface soils. Consequently, fields that were pleasing to the eye last week can turn ugly almost overnight if it struggles through the important transition period."
But, the timing of any of these conditions cane mean the difference between a crop that's slowed down and one that's dismantled altogether.
"Severe stresses that injure the seed or mesocotyl prior to a successful transition to the nodal root 'life support system' will kill or severely stunt a corn plant," Nielsen says. "The reason that seedling blight has been so devastating in recent weeks is the fact that the crop was young enough that it had not yet transitioned to full nodal root support and, thus, was vulnerable to damage to the mesocotyl or seed."
