Corn is used in more than 500 ways. It is grown primarily as a food source, but industrial uses include filler for plastics, explosives, dyes, insecticides and antifreeze. The United States is the world's biggest supplier of corn and corn products, accounting for 15.1 billion dollars annually. Organic corn production has become more vital each year as the demand for chemical-free products grows. Weed control is a primary concern for both types of corn production.
History of Corn
Corn is indigenous to the Western Hemisphere. An 80,000-year-old corn pollen sample was found in an excavation site at Mexico City. Petrified corn cobs identified by radiocarbon dating were found to be 5,600 years old. Historians believe that corn was first cultivated in the Tehuacan Valley of Mexico and that the original wild species has long been extinct. Corn in the Western Hemisphere is called "maize." European countries use the word "corn" for wheat or oats.
History of Weed control
Central- and American-Indian mound-planting methods provide weed control through companion planting. Corn is planted with beans and squash. The large, broad squash leaves block sunlight and prevent weed germination. Cultivated corn began to be planted in rows to make weed control easier for large crops of corn. Mechanical cultivators churn up soil to prevent weed germination and kill weeds already growing. Row width was dictated by the width of the horse-drawn cultivator. Row spacing is still dictated by the tire size of mechanical weed control cultivators.
Development of Herbicides
Technological advances of the 1940s changed the history of weed control. The first widely used weed killer was 2,4-D, manufactured by the Sherwin-Williams Paint Co. It is an effective, selective herbicide that is still in use today. In the 1970s, glyphosate-based Roundup was introduced by the Monsanto Co. and is now the leading weed control product worldwide. The inert ingredients in glyphosate herbicides were found to cause reproductive cell abnormalities in a 2009 study at the University of Caen, France.
The development of chemical weed control in corn led to the development of genetically modified corn and other crops. Transgenic corn has an artificially inserted gene that makes it able to resist the effect of herbicide. The producers of glyphosate herbicide also produce the genetically modified seed corn that farmers must use in tandem. Weeds that were formerly killed by glyphosate herbicides have become resistant to them, and many farmers have had to resort to other methods of weed control.
Sustainable Weed Control Methods
Rather than relying completely on synthetic herbicide weed control, many corn producers practice methods of sustainable agriculture. Herbicide effectiveness is increased when additional methods of weed control are used. Diverse crop rotations of soybeans, oats, wheat and hay cycle nutrients, reduce weed growth and add to biological diversity. Growing cover crops between corn crops also reduces the weed population.