Amy Brothers, age 13, of Hutchinson, Kan., for her question:
HOW IS HYBRID CORN FERTILIZED?
Corn is a cereal grass that is widely grown for food and livestock fodder. The fertilization of the corn plant is a complicated yet basically simple procedure that is handled by nature. The fertilization of hybrid corn requires the careful work of farmers.
The main stalk of each corn plant terminates in a tassel called a staminate (male) inflorescence. The tassel is made up of many small flowers termed spikelets. Each spikelet bears three small anthers which produce the pollen grains, or male gametes.
The pistillate (female) infloresence or ear is a unique structure with up to 1,000 seeds borne on a hard core called the cob. The ear is enclosed in modified leaves called husks.
The individual silk fibers that protrude from the tip of the ear are the elongated styles, each attached to an individual ovary. Pollen from the tassel is carried by the wind and falls onto the silks, where it germinates and grows down through the silk until it reaches the ovary. Each fertilized ovary grows and develops into an individual kernel on the cob.
The most important advance in the cultivation of corn was the introduction of hybrids. To produce hybrid corn, which yield more than ordinary varieties, breeders first produce pure strains, or plants that have the same characteristic year after year. They do this by inbreeding, or fertilizing a plant with pollen from the same plant.
Breeders take pollen from the tassel of a corn plant and place it on the silk of an ear of the same plant. Plants grown from seeds produced by inbreeding are called inbreds.
Inbreds are used only for breeding. However, by cross fertilizing plants from two different inbred lines, breeders can produce plants that are better than either parent.
Corn from a crop of hybrid corn cannot be used for seed, because it produces a crop with a lower yield. New hybrid corn seed must be produced and used every year.
Since the 1930s, the production of hybrid seed has become an important commercial industry.
Corn plants need rich, well drained soil. Farmers often improve soils with manure or artificial fertilizers.
One of the most common methods of planting is the hill check method. Two to four seeds are dropped into hills spaced three to four feet apart. This type of planting lets the farmer cultivate ail around the hills.
Farmers in drier areas use the listing or lister method of planting. A machine called a lister opens a furrow and drops the seed into it. The bedding method resembles listing except that the seeds are planted on the ridges instead of in the furrows.
More than nine tenths of the corn grown in the United States is hybrid. Its use is rapidly increasing in other important corn growing areas of the world.
Approximately 64 percent of the corn sold by farmers in the United States is used as livestock feed. About half of that amount is fed directly to hogs, cattle and poultry and the rest is used in mixed feeds. About 27 percent is exported and the remaining nine percent is sold as food.