Purdue University Department of Agronomy

Corny News Network

Originally published 1995, updated June 2009
Ugly duckling
URL: http://www.kingcorn.org/news/timeless/UglyDuckling.html

Corn And The Ugly Duckling

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen at purdue.edu
 

What little corn that was planted back in late April and early May is beginning to reach an important milestone in its growth and development. Recognition of this event helps explain the annual transition from a slow-growing, often ugly, field of corn to one that grows like wildfire.

Every year, for the first five weeks or so after corn planting is finished, the guys down at the Chat 'n Chew Cafe complain royally about the looks of the crop. Gripes about uneven stands, poor color, and slow growth abound around the tables as everyone airs their concerns about the looks of their neighbors' fields.

Then suddenly one day, the tone of the conversation in between the coffee and sweet rolls perks up. Almost overnight, the crop has taken off like a rocket. The color of the leaves turns a dark, almost-blue green and they develop a distinct shine. From that point on, any connoisseur of corn feels better about life in general. What happens?

During the first five weeks or so after planting, the corn plant is going about the business of creating all of the leaves it will ever have. A few of these leaves are visible, but most are wrapped tightly deep inside the whorl, biding their time until its their turn to emerge.

Some root development is also occurring during these same first five weeks. In fact, the successful development of the first three or four sets of nodal roots during this time will go a long ways to ensuring successful stand establishment of the crop.

Even though new leaves and some roots are developing during this time, the rate of increase in total plant dry matter is relatively slow. The photosynthetic 'factory' is small, as is the size of the raw material accumulator devices (the roots).

Once the corn plant reaches the five or six leaf stage (determined by number of visible leaf collars), a miraculous turn of events occurs. The final leaf is created at the main growing point of the plant (near the top of the 'pyramid' of stalk tissue) and the plant turns its attention toward developing the reproductive structures known as the tassel and ears.

At the same time, the size of the photosynthetic 'factory' and its supporting staff of roots is reaching a critical mass that is finally capable of manufacturing greater and greater amounts of energy. With greater amounts of available energy, the 'factory' begins to convert more and more of the incoming nutrients and carbon dioxide into sugars, starches, and other plant dry matter.

Subsequently, the stalk begins to elongate rapidly, the roots begin to develop rapidly, the tassel develops rapidly, the tiny ears within the ear shoots develop rapidly, and suddenly the plant is growing like wildfire. From about knee-high corn to the onset of pollination, the corn crop progresses through its most rapid growth phase (above- and below-ground), including the uptake of the lion's share of soil nutrients for use during the grain fill period.

By now you may be wondering what's the moral of this story? Primarily, it's a reminder to take time once in a while to look at this King of Crops in awe and wonder. Secondarily, be reminded that an ugly duckling of a corn crop that reaches the five to six leaf stage in reasonably good condition will usually turn the corner and become a beautiful swan of a corn crop during the next few weeks.

Thirdly, be reminded that true yield potential is just beginning to be determined at the start of this rapid growth phase. Ugly corn up to this point in time has not necessarily lost its yield potential. Ear size is determined from about knee-high to shoulder-high corn. Weather during pollination and grain fill finish off the yield determination. While we often moan and complain about the looks of young corn, it often surprises us with acceptable yields in the fall.

Related References

Nielsen, RL (Bob). 2007. Ear Size Determination in Corn. Corny News Network, Purdue Univ. [online]. Available at http://www.kingcorn.org/news/timeless/EarSize.html [URL accessed June 2009].

Nielsen, RL (Bob). 2008. Growing Points of Interest. Corny News Network, Purdue Univ. [online]. Available at http://www.kingcorn.org/news/timeless/GrowingPoints.html [URL accessed June 2009].

Nielsen, RL (Bob). 2009. Root Development in Young Corn. Corny News Network, Purdue Univ. [online]. Available at http://www.kingcorn.org/news/timeless/Roots.html [URL accessed June 2009].