Corn & The Environment

Corn & Photosynthesis

The process of photosynthesis by which green plants use sunlight energy to convert water and carbon dioxide into oxygen and organic compounds is the basis for virtually all life. Sugars, which are the first products of photosynthesis, are converted into starch, protein, oil, cellulose, lignin, and thousands of other chemical compounds.

Photosynthesis is also the source of the oxygen which we breathe. Indeed, before plants appeared, the earth's atmosphere was high in carbon dioxide but contained no oxygen. The present atmosphere, by comparison, is about 0.035% carbon dioxide and 21% oxygen - thanks to photosynthesis.

Some plant species are much more efficient than others in converting carbon dioxide and water into oxygen and organic matter - especially when the atmospheric concentration of carbon dioxide is very low as it has been for the past several hundred million years. These more efficient plants, which include corn, sorghum and a few weed species, have a unique "C4" photosynthetic system which permits carbon dioxide to be converted into organic matter at a faster rate than with the more common photosynthetic system of other plant species.

Why corn produces high yields

The presence of this efficient photosynthetic system and a long period of seasonal growth are important reasons why corn produces such high yields of organic matter (biomass) per hectare of land area per year, relative to most other plant species. In Ontario, for example, average grain yields with corn are about double those of other grain and oilseed crops (See table below). Forage (total above-ground) yields for corn are also normally higher than for other forage crops. The annual biomass production of a typical corn crop is about double that of an average temperate- climate forest (Cannell, 1989).

An average hectare of corn produces enough oxygen per hectare per day in mid summer to meet the respiratory needs of about 325 people. This means that the one million or so hectares of corn grown in Ontario produce enough oxygen for the annual respiratory needs of Ontario's 10 million residents in about 11 summer days!