Brought you by: Jonah T. Johnson, MS, CPAg, CCA - Sales Agronomist, PCT | Sunrise

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April 18, 2019: With the on-set of corn planting, the next question you get is “How long does it take corn to emerge?”  

A Few Items to Keep in Mind

1. Imbibe 30-35% of kernel weight in water           
   1. Imbibitional chilling-absorbing cold water and causing emergence issues
   2. Important to have good seed to soil contact 


2. Soil Temps at least 50 degrees Fahrenheit
   1. Radical elongation
   2. Seminal roots- cease growth at V3 and nodal roots (a.k.a. “adult roots” begin to emerge
   3. Energy is coming from endosperm (a.k.a. the seed reserves) 


3. VE-Mesocotyl pushes Coleoptile through the soil surface
   1. 90-120 growing degree day’s (GDD) to emergence
   2. Crown and Nodal root are at .75 inches below soil surface
      1. Influenced by sunlight
         1. Very shallow planting depths will not have crown or mesocotyl
         2. Deeper planting depths have more consistent temp and moisture
      2. The growing point and leaf initiates elongate upward from this point
   3. Large percentage of energy is still coming from the endosperm
      1. A small portion is being supplied by the seminal roots and first nodal roots
      2. The mesocotyl transports nutrients from seminal roots and endosperm to the leaves.
      3. Starter can provide a more vigorous, healthier start.


4. V5 growing point breaks soil surface    
   1. Susceptible to death from frost, other physical damage.

And A Deeper Dive into Determining Corn Emergence
 
Corn typically requires 120 growing degree units (GDU) to emerge. 
 
As temperatures increase, the process required for germination to proceed occurs at a faster rate, leading to more rapid emergence. Under ideal conditions, corn will emerge in ten days or less, but with cooler soil temperatures the process may take three weeks or longer. Environmental and management factors influence the number of GDUs required for emergence. If heavy residue is present in conservation tillage systems, emergence can take an additional 30 to 60 GDU’s simply because soils are cooler. 

To Calculate GDU’s

• Take the Daily High – 50 + Daily Low – 50 then divide by 2. 
• If the daily temp is 75 for the high and 60 for the low, ((75-50) + (60-50)) /2 = 17.5 GDU’s. 
• Any high temps above 86 degrees will be calculated using 86 degrees.

 

Growing Degree Unit (GDU) adjustment for various environment characteristics and management practices
Environment Characteristic / Management Practice	GDU Adjustment
Conservation tillage (more than 75% residue)	Add 30-60 GDU
Soil texture: Fine	Add 30-60 GDU
Soit texture: Coarse	Subtract 30-60 GDU
Seed zone soil moisture (below optimum)	Add 30 GDU
Seedbed condition (soil crusting or massive clods)	Add 30 GDU
Seeding depth (for each inch below 2 inches)	Add 15 GDU
Hybrid differences for emergence	Hybrid specific
Chart from University of Wisconsin, 1997.

 

What Distinguishes an Emerged Plant?

When the coleoptile (or spike) breaks through the soil surface and encounters light, coleoptile and mesocotyl elongation stop. The coleoptile ruptures allowing the first leaf to emerge. At this time the location of the growing point and nodal root system is set.

With a planting depth of 1½ inches or more, the growing point is set approximately ½ to ¾ inch deep. Floppy or rootless corn can occur when the growing point is too shallow and the nodal root system is initiated on the soil surface.

This is often the result of either shallow planting or soil settling or eroding away from the base of the plant after the growing point has been set. A pre-plant application of a growth regulator herbicide like 2,4-D can also cause elongation of the mesocotyl and force the nodal roots to develop above ground, leading to rootless corn syndrome.