Inside Grundy County
By Patrick Derdzinski, Grundy County Extension Director
April 19, 2010
Corn: History, Facts and Trivia
In 2009, Iowa farmers grew 13.4 million acres of corn at an average yield of 182 bushels per
acre. These 2.44 billion bushels of corn were valued at 9.146 billion dollars. This data illustrates
why corn is of great importance to our rural communities and state economies, and is sometimes
referred to as king corn. Corn began as human food staple, then used in large quantity by the
livestock industry and now a large percentage (>30%) of corn is grown for fuel. But where did
corn come from? How does the corn plant grow?
Corn, or maize, is officially Zea mays, a member of the plant family, Gramineae. In other words,
corn is a grass. Corn is thought to have originated from teosinte. Teosinte, Zea Mexicana, is a
wild grass that has a single row cob. It was thought to have been crossed with another grass and
then back crossed. But the true parentage is not been verified.
Archeological evidence indicates corn became domesticated around 5600 years ago in Central
America and Mexico. Some historians narrow the first domestication of corn to the Tehuacan
valley of Mexico. The first corn type seeds found in caves had floral bracts (modified leaves)
covering the kernel. As time progressed, the size of ears increased and the bracts decreased
indicating selection pressure by man.
Native Americans aggressively selected corn with continued improvement from around 3400
B.C to 1500 A.D. Native Americans were so efficient with selection that corn adapted to thrive
under varying climatic conditions. Prior to the Europeans arrival in North America, corn was
being grown from southern N. Dakota, along the St. Lawrence valley, westward to Kansas and
south to Arizona, New Mexico and south all the way to Northern Argentina and Chile, including
the Andes highlands.
Differentiation of corn types occurred, influenced by the type of endosperm (starch) and glumes.
There were seven different groups of corn called dent, flint, flour, popcorn, sweetcorn, waxy and
pod corns. Dent corn is the most widely grown in the U.S. As the inner soft starch (endosperm)
dries, it shrinks and a dent occurs on the top of the kernel. Flint corn has a soft starch in the inner
kernel surrounded by a hard layer called a corneous layer. Flint corns are usually rounded at the
tip. Most flint corn is now grown in South America.
Flour corn has soft starch like dent corn but it much more of the kernel is filled by the soft starch
and the kernel tip is also somewhat rounded. In the US, we refer to this corn as blue corn which
is made into some tortillas and chips. Popcorn is very small kernel with an extremely hard,
corneous endosperm. When heated, moisture inside the kernel explodes, expulsing white starch
many times its size.
Waxy corn has a soft endosperm containing amylopectin. Most corn has two forms of starch,
amylopectin (78%) and amylase (22%). I waxy corn, it’s essentially 100% amylopectin.
Amylopectin is a branched form of starch, is “sticky” and used in special foods or adhesives.
Sweet corn has a high concentration of sugars when in the milk stage. There are different genes
that control this. Modern development has resulted in varieties that are sweeter and maintain the
sweetness for a longer period of time.
Corn is considered an annual, warm season grass. It prefers a mean summer temperature of 70°F
to 80°F with a mean night time temperature over 58°F. It can grow in regions receiving 10” of
rainfall to areas with 200” of rainfall. In the Midwest, corn will produce well if we receive
around 25” of precipitation.
Corn is a monoecious plant, which means it has separate female (ear) and male parts (tassel) on
the same plant. Corn is genetically considered a diploid which means it has 2 pairs each of 10
chromosome for a total of 20 chromosomes.
Original corn varieties were open pollinated plants which meant we relied on mother nature to
cross the plant. Farmers selected the most vigorous ears for planting the following year. Now we
use a process called hybridization to develop new varieties. Modern science has allowed us to
insert genes into corn which has improved insect resistance in our modern corn hybrids.
The selection process is still being carried on by modern science. But because of thousands of
years of continuous selection by man, it is believed corn cannot survive without human
cultivation. However, because of continuous selective improvement, corn is more extensively
distributed around the world than any other cereal crop. It is now used for many items, from
human consumption to animal feed, for ethanol production to making plastics, baking products,
soaps, solvents, adhesives, herbicides and much more.